1
Q
What material is the cell wall of algae made of?
A
Cellulose
2
Q
One of the functions of ATP, apart from hydrolysis to form ADP + Pi to release energy, is ____ to ____.
A
phosphorylating other biological molecules to make them more reactive.
3
Q
First, to control the transcription of one or more structural genes in prokaryotes, the regulatory gene produces a/an ____. Next, this protein binds to the ____. As a result, the ____ is unable to bind to the ____. Fourth, this prevents the RNA polymerase from ____.
A
repressor transcription protein, operator, RNA polymerase, promoter, transcribing the structural genes
4
Q
What does an operon contain?
A
A cluster of structural genes, a promoter and an operator (it typically does not contain the regulatory gene itself).
5
Q
At the post-transcriptional level, how is protein synthesis regulated?
A
Via the rate of mRNA editing; a higher rate means more mature mRNA is available for translation.
6
Q
Active gene
A
A gene that is transcribed and translated.
7
Q
Human genes can be inserted into the bacterial DNA. These genes can then be translated in bacteria to produce human proteins, such as insulin.
Explain why this is possible. [2 marks]
A
The genetic code is universal / the same triplets / codons code for the same amino acids (in all organisms);
Transcription/translation mechanisms are universal.
8
Q
Suggest two benefits of sequencing the entire human genome. [2 marks]
A
- Helps in the development of personalised medicine
- Can produce more targeted / more effective medicines
- Can be used to trace evolutionary relationships
- Useful for diagnosis / treatment of diseases
- Better understanding of which genes are responsible for certain diseases
9
Q
State two reasons why new genetic sequencing technology is more advanced than the technology used in the Human Genome Project. [2 marks]
A
- Cheaper
- Faster
- More accurate
- Generates more data / more complete sequence
- Can be done with smaller machines
- More automated / requires less specialist training
- Can process multiple samples at once / is more efficient
10
Q
LacY gene
A
A structural gene which binds to RNA polymerase during transcription of a protein to facilitate the transport of lactose into a bacterial cell (the lactose permease protein)
11
Q
LacI gene
A
Regulatory gene that codes for the lac repressor transcription factor
12
Q
Regulatory gene in lac operon name
A
LacI
13
Q
Structural genes in lac operon names
A
lac Z/Y/A
14
Q
Explain why the lac operon structural genes aren’t always expressed. [2 marks]
A
The structural genes coding for lactose digestion are only active when lactose is present, and so ensures that ATP isn’t wasted on expressing the genes coding for lactose digestion when lactose isn’t present.
15
Q
What type(s) of organisms have operators?
A
Eukaryotes don’t have operators (whereas prokaryotes do)
16
Q
Plants can reproduce without fertilisation to produce genetically identical clones. What is this type of natural plant cloning called?
A
Vegetative propagation
17
Q
A clone is produced using an underground horizontal stem with lateral shoots and roots at intervals called a/an ____.
A
rhizome
18
Q
Examples of rhizomes
A
Bamboo, ginger
19
Q
Corm
A
A short, vertical, swollen, underground plant stem base that serves as a storage organ
20
Q
Difference between a corm and a bulb
A
Bulbs are made of layers of fleshy leaves, whereas a corm is a swollen stem
21
Q
For speciation to take place, there must first be ____.
A
reproductive isolation
22
Q
Describe how biologists carry out micropropagation. [4 marks]
First, a small sample of ____ tissue, called a/an ____, is taken from a healthy plant.
Then, the sample is ____ (with ____) to reduce the chances of contamination, among other ____ techniques.
It is grown on ____ ____ with a ____ ____ (containing e.g. ____). A mass of cells, called a ____, grows.
Finally, this mass of cells is divided and grown in new cultures with ____ to form ____, which are potted in soil.
A
meristem, explant, sterilised (ethanol), aseptic, agar gel, nutrient medium, glucose [for respiration] amino acids [for protein synthesis] phosphates [for DNA/ATP], callus, hormones, plantlets
23
Q
In micropropagation, what do the hormones added help with?
A
Cell differentiation or (shoot/root) growth.
24
Q
In germ-line gene therapy, the gene is introduced into ____.
A
germ cells (also called sperm and egg cells)
25
Currently, only gene therapy targeting somatic (body) cells is legal. Suggest why gene therapy targeting germ cells (gametes) is currently illegal. [1 mark]
Changes in the genome/gene sequence/genes/ to the DNA of gametes is permanent/can be passed onto offspring.
26
SCID can be caused by mutations in the ADA gene which encodes the adenosine deaminase (ADA) enzyme. The ADA enzyme is expressed in T cells and is important for their function. Patients with SCID have a non-functional ADA enzyme.
Explain how reimplantation of modified T cells back into the body can temporarily cure a SCID patient. [3 marks]
* ADA enzyme produced (in modified T cells)
* Functional T cells **activate B cells**;
* (So) normal adaptive immune response [producing specific plasma + memory cells]
27
Give two reasons why it is easier to obtain genes from mRNA, rather than directly from the DNA removed from human cells. [2 marks]
* mRNA is **present in larger amounts**;
* mRNA has been edited/**does not contain introns**;
* mRNA **codes for a single protein**.
28
myogenic
Does not require nervous stimulation for contraction.
29
Suggest and explain one way in which the student measuring arm muscle fatigue could have improved the method used to investigate muscle fatigue. [2 marks]
Repeat the experiment with different muscle groups (not just hand muscles);
Because different skeletal muscles may fatigue at different rates.
30
Explain why skeletal muscle fatigues over time. [4 marks]
-(Because) **lactate produced** (after repeated contractions);
-Due to **anaerobic respiration**;
-Lactate **lowers pH of muscles** (which affects contraction);
-Fewer calcium ions available/calcium ion stores depleted (after repeated contractions);
-Calcium ions needed in muscle contraction;
31
When the cell is at rest, ____ K+ channels are open so ____ diffuse ____ the cell through these channels.
**most**, some, out of
32
ring rot
bacterial disease that kills potatoes and tomatoes
33
late/potato blight
Fungus-like protoctist disease that affects plants
34
Mutations can be caused in which two ways? Describe how
Naturally (when DNA breaks down or when polymerase enzymes insert the wrong nucleotides/the wrong number of nucleotides so DNA isn't copied accurately)
By external factors: a mutagen reacts with DNA and changes some nucleotides' structures/causes the DNA to break down (and these changes aren't repaired by the cell)
35
Hox genes are found in ____.
Hox genes are **only** found in animals.
36
mitosis purposes
* **asexual reproduction** in plants
* production of new stem cells
* producing **gametes from *haploid cells***
* proliferation of white blood cells
37
How does the structure of an arteriole compare to the structure of an artery?
* Compared to arteries, arterioles have a thicker muscle layer.
* Arterioles have a thinner elastic layer.
38
How is the artery wall adapted to its function?
The wall is thick to help prevent the artery from bursting under pressure.
39
Blood vessels generally contain an elastic layer. What is its function?
To **stretch and recoil** to **maintain blood pressure**.
40
What is the muscle layer and elastic layer's function in blood vessels?
To contract to **control the flow of blood**.
41
Suggest when gene mutations are most likely to occur. Explain your answer. [2 marks]
Synthesis stage of the cell cycle, as it is undergoing DNA replication / longest stage.
42
Direction of Na+ K+ pump
3 sodium ions OUT of the cell and 2 potassium ions INTO the cell per cycle
43
When, where and why is ABA produced?
ABA is produced in roots/leaves during times of water stress and triggers stomatal closure to conserve water.
44
How does ABA affect stomatal closure?
* ABA binds to receptors on guard cells plasma membranes.
* This stimulates Ca2+ ion channels to open, allowing them to move into the cytosol (part of the cytoplasm) from the vacuole.
* This opens other ion channels in the plasma membrane.
* This causes an efflux of ions out of the guard cell, **increasing the water potential inside the guard cells**.
* This causes water to leave by osmosis, making the cells flaccid and the stomata close.
45
How does ABA affect seed germination? Explain how.
ABA inhibits seed germination and maintains dormancy by **inhibiting amylase production**, opposing the effects of gibberellins.
46
Gibberellins ____ stomatal closure.
stimulate
47
Outline the roles of synapses in the nervous system. [3 marks]
* **Cell signalling** (by passing on APs from one cell to the next)
* Unidirectional transmission
* Convergence & divergence
* Lots of low-level stimuli to be **amplified**
* Only strong enough stimulations are passed on -> prevents overstimulation of the postsynaptic neurone
48
How are action potentials ensured to travel in one direction only?
Presynaptic neurone **axon membrane** is hyperpolarised and so **unresponsive**.
49
Stroke volume
The volume of blood pumped out of the left ventricle each beat.
50
The Bohr effect is beneficial for exercise. Explain how.
Respiring muscle cells release carbon dioxide, which decreases the pH of the blood near the tissues.
This causes haemoglobin to change shape, allowing oxygen to dissociate more readily.
This means cells are provided with more oxygen for aerobic respiration.
51
Oxygen association and dissociation are both examples of ____.
positive cooperativity
52
Oxyhaemoglobin dissociation curves have ____ on the y-axis and ____ on the x-axis. There are *gentle/steep positive/negative* gradients at the top and bottom with a *gentle/steep positive/negative* gradient in the centre
% saturation, partial pressure of oxygen, gentle positive, steep positive.
53
Give two limitations of using respirometers to investigate respiration rate.
Oxygen uptake is not a good representative of the rate of respiration.
Oxygen may leak out of the respiratometer through connecters, decreasing the fluid marker movement.
54
You want to investigate the respiration rate of a woodlouse and beans. What might you want to control?
Mass of organisms
Temperature
Light intensity
Soda lime mass
55
At 90s, the respirometer meniscus is at 31.0, 32.0 amd 32.5mm through the capillary tube for the three trials. At 150s, the meniscus is at 53.0, 54.0 and 53.5mm. Calculate the mean rate of respiration between these times.
Distances travelled = 22, 22 and 21mm
Mean distance travelled = 21.666...mm
Mean rate of respiration = 21.666... / 60 = 0.3611... ~ 0.36mm/s
56
Explain how the Casparian strip prevents ions from reaching the xylem of the plant by the apoplast pathway. [2 marks]
The Casparian strip is impermeable/impervious to water/solutions, so forces water/solution to pass through the plasma membrane - the plasma membrane repels ions.
57
'Anaerobic' bacteria suggests what?
The bacterium doesn't require oxygen for respiration - absence of oxygen is preferred/essential.
58
Botulism prevents the release of neurotransmitters at cholinergic nerve terminals of stimulatory motor neurones. Explain why botulism can be fatal.
Intercostal/diaphragm muscles become paralysed or are weakened.
Ventillation and oxygen concentration of the blood decreases.
Cells/organs can't obtain oxygen for aerobic respiration.
59
Toxins are what?
Antibodies (proteins)
60
Explain how toxins are dealth with by the immune system.
* Antigen presenting cells (APCs) ingest antigens, process them and display them on their surfaces.
* T helper cells with complementary receptors to these antigens interact with them, producing interleukins.
* T helper cells also activate specific B lymphocytes with clonal selection followed by clonal expansion.
* B lymphocytes differentiate into plasma cells, which produce antibodies (antitoxins) that bind to and neutralise the toxins.
61
Vesicle types
Secretory vesicle (for exocytosis)
Transport vesicle (for movement across the cytoskeleton)
62
How do vesicles move around inside a cell?
Vesicles attach to the cytoskeleton and are moved by protein motors / change in microtubule length (contraction)
63
In which stage(s) of aerobic respiration is there a net yield of
2 ATP molecules?
Glycolysis, Krebs cycle (1 ATP per cycle, but this happens twice for each glucose molecule).
64
RQ = ?
carbon dioxide produced / oxygen consumed
65
lipid, carbohydrate and protein RQ values
Lipid: 0.7
Carbohydrate: 1
Protein: 0.9
66
The student repeats the respirometer experiment with a cricket.
Crickets have a **higher** respiratory quotient than grasshoppers.
How would the results from the experiment using a cricket be different to using a grasshopper? Explain your answer.
A higher respiratory quotient means that the cricket requires **less** oxygen for respiration than the grasshopper.
This means the volume of air in the tube decreases less with the cricket, so the coloured liquid moves less far to the left.
67
Photolysis takes place in the ____.
thylakoid space
68
Once electrons in chlorophyll are lost during ____, they are replaced in ____. In this reaction, light splits water into electrons, protons, which ... , and oxygen, which ...
photoionisation, photolysis, maintain the high concentration in the thylakoid space, diffuses out of the plant or is used in respiration
69
recessive epistatic allele ratio
dom both : dom epi only: rec epi
9 : 3 : 4
70
dominant increases the lifespan of trees
dom epi : rec epi only : rec both
12 : 3 : 1
71
Is coppicing labour-intensive?
Yes - coppicing requires skilled workers to carry out the cutting and harvesting.
72
Does coppicing increases the lifespan of trees?
Yes - coppicing triggers rapid regrowth from the established root system and prevents the tree from becoming top-heavy, senescent (growing old so cells are less able to divide successfully) and decreasing the likelihood of becoming diseased. This means coppicing allows the tree to "reset" its age repeatedly.
73
Where are neurotransmitters found in a synapse?
In **synaptic** vesicles.
74
An action potential reaches a synaptic knob. What happens next?
**Voltage-gated** Ca2+ channels open.
75
ACh is an ____ neurotransmitter.
excitatory
76
What **type** and **sorts** of neurotransmitters are released at a neuromuscular junction?
Only excitatory neurotransmitters, but they're not just ACh.
77
What does a neuromuscular junction join?
A motor neurone to a muscle cell.
78
What happens at inhibitory synapses?
Neurotransmitters bind to receptors on the post-synaptic neurone membrane, opening chloride ion channels. Chloride ions move into the post-synaptic neurone, hyperpolarising the post-synaptic membrane and causing the postsynaptic neurone's potential difference to decrease below its usual resting potential.
79
One Na+ ion channel has spaces for ____ neurotransmitter molecule(s) to bind.
two
80
How is ACh broken down, and how is it reformed?
ACh -> **choline and ethanoic acid**
These diffuse into the pre-synaptic neurone and are recombined to form ACh.
ACh is then actively transported into synaptic vesicles.
81
When is ACh an inhibitory neurotransmitter?
In the heart, where it causes** potassium ion channels** to open, hyperpolarising the postsynaptic membrane.
82
What type**s** of responses are mainly used by endotherms to help them warm up and cool down?
Behavioural responses and physiological responses - metabolism
83
Describe the conditions that create a diffusion gradient for oxygen in the insect gas exchange system. [2 marks]
Aerobic respiration in insect muscle tissue uses oxygen.
This makes the oxygen concentration **inside the insect lower** than the oxygen concentration of the air outside.
So there is an oxygen concentration gradient from the air into the tissues
84
Homologous pairs
Two chromosomes which have the same set of genes (but not necessarily alleles).
85
Why is transmission of the impulse from the SAN to the Purkyne tissue is slightly delayed?
To allow time for the **atria** to fully empty.
86
How might officials at ports support sustainable fishing?
Officials carry out **catch inspections** to enforce protection measures (e.g. fish quotas).
87
Which type of muscle is multinucleated (has more than one nucleus)?
Skeletal
88
What is a unique feature of cardiac muscle cells? **Explain the use of these.**
Cardiac muscle cells are connected with intercalated discs - these have **low electrical resistance** so nervous impulses pass easily between the cells and **helping coordinate heart contractions**.
89
Phagocytes have receptors complementary to ...
molecular patterns
90
Lymphocytes have receptors complementary to ... (2)
antigens presented on antigen-presenting cells (phagocytes) - T lymphocytes
antigens on pathogens - B lymphocytes
91
Hox genes control ...
**symmetrical** body plan development in animals
92
The homeobox of a Hox gene codes for a ...
homeodomain
93
Enzymes can be activated by the addition of a ____ ____ in ____ from a molecule of ____.
phosphate group, phosphorylation, cAMP
94
After transcription, the mRNA is called _ /_ mRNA.
pre- / primary
95
Suggest one reason why scientists doubted for a long time that DNA is the store of genetic information in all living organisms. [1 mark]
The structure of the DNA molecule is very simple.
96
DNA is ____ than RNA.
longer
97
Give two ways in which cells defend against the damaging effects of DNA base changes. [2 marks]
Degenerate / redundant genetic code (allows silent mutations);
DNA repair (during G2 phase - G2 checkpoint).
98
mass flow
Movement of assimilates from a high concentration (+pressure) to a low concentration (+ pressure) down the pressure gradient from source cells to sink cells.
99
Substrate-level phosphorylation and oxidative phosphorylation are two ways of producing ATP. Contrast these different forms of ATP production. [3 marks]
| Less common ones.
Less common ones:
Substrate-level phosphorylation does not involve electron transport chain;
AND
Oxidative phosphorylation does
Substrate-level phosphorylation does not use
NADH/FADH2
AND
Oxidative phosphorylation does
Substrate-level phosphorylation occurs under aerobic and anaerobic conditions;
AND
Oxidative phosphorylation only occurs under aerobic conditions
100
Suggest an advantage of oxidising lactate in muscle cells. [2 marks]
Lactate (and/or) pyruvate are energy sources;
Muscles have an immediate energy/ATP supply near to the site where it's needed.
101
What cells do germ line therapy treatments affect?
Gametes
102
Compare somatic cell gene therapy with germ line gene therapy.
* Germ line is permanent whereas somatic cell is temporary so needs repeating
* Germ line stops the individual's offspring from having the faulty allele/condition, whereas somatic cell only affects the individual
* Somatic cell affects only some (certain ones) of the individual's cells, wheras germ line affects all of the individual's cells.
103
How are samples collected and treated in micropropogation?
Tissue culture is taken from meristem tissue, **sterilised** (e.g. with ethanol) and grown with **hormones + nutrients** until roots develop.
Callus formed is split into cells, which are separated on new agar plates.
This is repeated for mass plant reproduction.
104
In artificial twinning, how are many eggs stimulated to be released?
Female is given hormones to stimulate her to produce and release many eggs.
105
What are the two animal cell cloning methods?
Somatic cell nuclear transfer (SCNT)
Embryo splitting / artificial twinning
106
Which method was used to make Dolly the sheep?
SCNT
107
Why is it thought that Dolly the sheep had a shorter life span?
Clones made from SCNT receive **adult DNA damaged from many replications** of the biological parent cell (it has already aged).
108
SCNT two terms to describe egg cell that is removed
Oocyte (immature egg cell)
Enucleated (nucleus removal)
109
Disadvantages of animal cloning (4)
* SCNT is **inefficient** (many eggs are needed for a success)
* **High miscarriage rate** when implanting embryos in SCNT
* Thus it's time-consuming and expensive
* SCNT animals have a shorter lifespan
110
In the first step of the polymerase chain reaction, the DNA fragment is heated so that ____.
the strands separate
111
different individuals may have different numbers of repeats. This represents lots of variation, which is possible because ____.
non-coding sequences are not affected by (natural) selection
112
To make DNA fragments, STRs are cut out (____) with ____.
isolated, restriction endonucleases
113
Gel electrophoresis uses ____ gel.
Agarose gel (more purified than agar gel, with specific pore sizes)
114
Electrophoresis plate charges on either end
Samples move from the negative cathode to the positive anode.
115
How long is a voltage applied across the agarose gel?
Usually around 30 minutes to one hour.
116
The DNA bands from the agarose gel is transferred to ____. Explain why.
Sheet of paper / membrane
The agarose gel isn't very durable, so this allows the DNA fragments to be preserved.
117
What three things can gel electrophoresis separate?
DNA & RNA fragments, proteins.
118
What other processing do proteins need to undergo before they can be separated in gel electrophoresis?
Mixed with a chemical to denature the proteins so they all have the same charge (can be +ve or -ve -> makes them all -ve, of different magnitudes).
119
What is added to the DNA fragments to help visualise them?
DNA probes with a stain
120
What is a stain-like substance you can add to the electrophoresis plate (additional to DNA probes with a stain)? What else does this do?
Adding loading dye to the DNA samples in the wells.
Helps the samples sink to the bottom of the wells.
121
How do you add loading dye to the sample wells?
Use a **clean** **micropipette** each time, place the tip into the buffer solution just above the opening of the well (not too far to not pierce the bottom of the well).
122
Give two ways to produce DNA fragments, and what each method requires.
Using restriction endonucleases (length of DNA) or reverse transcriptase (mRNA strand, DNA nucleotides, another enzyme to remove mRNA strand, DNA polymerase).
123
Describe how reverse transcriptase works.
* Moves along an mRNA molecules, adding complementary DNA nucleotides to form a complementary DNA (cDNA) strand.
* A second enzyme removes the mRNA strand, leaving only the cDNA strand, with exposed bases.
* DNA polymerase moves along the cDNA strand to forms sugar-phosphate backbone of a second DNA strand.
* We now have a complete DNA fragment.
124
What forms between the complementary bases of the DNA fragment and plasmid?
Hydrogen bonds.
125
Why must you use DNA ligase in GE?
DNA ligase attaches the DNA fragment nucleotides to those of the pladmid. It then binds the nucleotides together by catalysing the formation of a phosphodiester bond.
126
Why don't plasmids tend to be absorbed by bacteria normally?
Plasmids contain DNA, which is polar, hydrophilic and has a negatively charged backbone, so are unlikely to pass through the bacteria phospholipid membrane.
127
What **two** ways can bacteria be transformed?
**Add calcium ions** to the bacteria with a **heat shock** (rapidly increasing the temperature).
Add an electric current to the bacteria - electroporation.
These both increase the uptake of plasmids.
128
How do calcium ions increase the uptake of plasmids by bacteria?
Ca2+ are positive, so are attracted by the negative charges of the plasmid DNA backbone and the phosphate heads in the plasma membrane.
Increase in temperature (heat shock) increases space between adjacent phospholipids - pores.
129
How can scientists identify which bacteria contain the recominant plasmid?
Cut open an antibiotic resistance (marker) gene in the plasmid with restriction endonucleases. Bacteria that contain a recombinant plasmid will die.
130
If using an antibiotic resistance marker gene to identify transformed bacteria, how can scientists get a sample of the transformed bacteria if they all die from testing them?*
## Footnote
*Don't need to know the process, it's just for understanding.
Replica plating is used.
Bacteria colonies are grown on an agar plate.
A new plate is pressed over the original plate to collect a sample of each colony, in the same position as the first plate. This second plate contains an antibiotic.
Identify colonies that die in the second plate; these have the recombinant plasmid.
Compare the two plates to identify which bacteria in the original plate contain the recombinant plasmid.
131
Marker gene definition (**two options**) + examples
An identifiable gene in a plasmid that another gene is inserted into **OR** that is inserted into a plasmid alongside a desired gene, to confirm successful genetic transformation.
Antibiotic resistance MG, fluorescent MG, enzyme MG
132
A gene is inserted into an antiobiotic resistance gene in a plasmid. How do you know if transformation was successful?
The former antiobitic resistance gene stops being expressed.
133
Vectors to make recombinant DNA with.
Plasmids or bacteriophages (viruses which infgect bacteria)
134
One farmer concluded that the increase in the use of GM crops had caused a mutation in one of the insect species that gives resistance to the Bti toxin, which then spread to other species of insect through mating.
Explain why the farmer is incorrect. [3 marks]
* Mutations are spontaneous / random and not caused by GM crops;
* **Different species of insects cannot interbreed** / produce fertile offspring;
* So **mutation / allele cannot be passed from one species of insect to another**.
135
What is *Agrobacterium tumefaciens* used for?
Infecting **plant** cells (in order to make GM plants).
136
How would you make a GM plant?
Isolate desired gene and insert into a bacterium's plasmid (*Agrobacterium tumefaciens*).
Put the pladmid back into the bacterium.
Infect plant cells with the transformed bacteria - the gene gets inserted into the plant cells' DNA.
137
Outline the negative ethical issues of Golden Rice. [3-4 marks]
* Public may not wish to consume GM crops/lack of knowledge of GM organisms;
* **Yellow colour of rice may mean people are reluctant to eat it**
* **Genetically modified seeds may be spread into neighbouring fields/genes may escape into the wild/cross-pollinate with other species to affect ecosystems**
* May have (as yet unknown) negative long term effects on the human body.
138
Outline the positive ethical issues of Golden Rice. [3-4 marks]
* Has been (rigorously) tested/no toxicity or allergy found;
* Golden Rice can be grown by existing rice farmers **without need for new equipment/training**
* (Genetically modified so) **rice seeds can be used for subsequent cultivation / no need to distribute seeds to farmers every year.**
* **Cheaper than using Vitamin A tablets/supplements**
139
How would you make a GM animal?
* Inject desired DNA fragment into an embryo and implant into a female animal.
* Test offspring to see if it can produce the desired protein.
* Selective breeding.
140
141
In DNA sequencing, which end of the electrophoresis gel is read first? Explain why.
Read from the furthest point along the gel back towards the negative cathode - smallest/shortest DNA fragments travel fastest and so the furthest towards the positive anode.
142
What is shown in Sanger sequencing from the DNA fragment bands?
The complementary DNA sequence.
143
A small section electrophoresis gel for a gene being sequenced reads TTCAAGA. What is the original DNA sequence?
AAGTTCT
144
In genome sequencing, what vector is used?
Bacterial artificial chromosomes (BACs) - man-made plasmids.
145
Each DNA fragment in genome sequencing is inserted into a ____ ____.
different BAC
146
Each BAC in genome sequencing is inserted into a ____ ____.
different bacterium
147
What are the steps to genome sequencing? (6)
1. Genome broken into smaller DNA fragments.
1. DNA fragments are inserted into different BACs.
1. BACs are inserted into different bacteria.
1. Bacteria divide, creating colonies of cloned bacteria each with a specific DNA fragment.
1. DNA is extracted from each colony and cut with restriction endonucleases.
1. DNA pieces are sequenced (chain-termination method) then put in order using computers. DNA fragments from all BACs are put in order to complete the whole genome.
148
Outline why the different BACs with different DNA fragments can be used to order a genetic sequence.
The DNA extracted from the bacterial colonies are cut with restriction endonucleases, producing **overlapping** pieces of DNA.
149
Epidemiological study
The study of health and disease in a population
150
Technology transfer
The sharing of information, technology and skills between institutions to develop products (e.g. GM products) faster.
151
What vectors can you use in gene therapy?
Plasmids, altered viruses or liposomes.
152
One negative ethical issue of gene therapy
Risk of harm e.g. gene overexpression leading to excess production of proteins.
153
Some non-ethical issues of gene therapy (3)
* Incorrect allele insertion into DNA may cause other issues e.g. cancer.
* Somatic therapy effects are short-lived, so patient may have to undergo multiple treatments.
* It may be difficult to get the allele into only specific body cells.
154
How do pheromones defend plants against herbivores?
Pheromones trigger nearby plant leaves to produce **more alkaloids**, which makes leaves harder to eat.
Callose reinforces plant cell walls, which makes them thicker.
This makes it harder for herbivores to eat leaves.
155
Microorganisms can be grown using ____ ____ at ____ temperatures. This increases/decreases the cost.
waste products, low, decreases
156
What are the three main waste products which need to be excreted in mammals?
Mammals need to excrete carbon dioxide, **bile** and urea.
157
In the fight or flight response, the hypothalamus activates part of the endocrine system called the ____ ____ system.
adrenal-cortical
158
Coppicing produces a variety of light levels. True or false?
True.
159
Disadvantage of clear felling
Removal of root stability causes soil erosion.
160
Why is it difficult to sustainably manage the fishing industry?
* The areas open to fishing are very large -> hard to monitor
* Catch inspections are expensive.
* Fishing companies falsely report the number of fish caught to avoid quotas.
161
The Apple Fly and the Hawthorn Fly are both native to North America. Apple flies are a pest of cultivated apple trees. They lay their eggs on apples. Hawthorn flies lay their eggs on Hawthorn fruits.
It is thought that the two fly species originally arose after the introduction of non-native apple trees about 200 years ago. Since this time, genetic differences arise between these two species. This is considered to be an example of the process of sympatric speciation.
Suggest how these two species of fly may have arisen by sympatric speciation. [6 marks]
1. Occurs in the **same habitat** / environment / population;
2. **Mutation(s)** cause differences in egg-laying locations;
3. Reproductive separation/isolation OR no gene flow OR gene pools remain separate;
4. Different allele(s) passed on/selected OR change in frequency of allele(s) (over time);
5. **Disruptive (natural) selection**;
6. Eventually different species cannot (inter)breed to produce fertile offspring.
162
Sickle cell anaemia is an inherited disease in which red blood cells are abnormally shaped. Sufferers have two copies of the recessive sickle cell allele and often die prematurely.
However, a single copy of a sickle cell allele allows for protection against malaria. The sickle cell allele is most abundant in areas where malaria is endemic.
Use this information to explain which type of selection is occurring in areas where the incidence of malaria is high. [3 marks]
Stabilising selection;
(Because) loss of recessive sickle cell allele through death of homozygotes is balanced by reproductive advantage of heterozygotes;
(So) frequency of recessive allele remains constant over generations.
163
Sickle cell anaemia is an inherited disease in which red blood cells are abnormally shaped. Sufferers have two copies of the recessive sickle cell allele and often die prematurely.
However, a single copy of a sickle cell allele allows for protection against malaria. The sickle cell allele is most abundant in areas where malaria is endemic.
Use this information to explain which type of selection is occurring in areas where there are no cases of malaria. [3 marks]
**Directional** selection;
(Because) recessive sickle cell allele causes the death of homozygotes / reproductive disadvantage (no benefit from having a single copy of the sickle cell allele as there’s no need for protection against malaria)
(So) frequency of recessive allele decreases over generations.
164
Explain how the different flowering times might eventually lead to the formation of a new species of Agrostis. [4 marks]
1. Reproductively isolated / no interbreeding (different flowering times);
2. Conditions different for two populations / different selection pressures;
3. Different features or plants are selected or survive / different adaptations;
4. Populations become (genetically) different / unable to produce fertile offspring.
165
In the north of the Pacific Ocean, scientists recognise two populations of killer whale: ‘R’ killer whales and ‘T’ killer whales. These two populations are the same species, and their habitats overlap.
Suggest why these two types of killer whale are treated as two different populations. [2 marks]
The two groups do not spend time together within their shared habitat;
The two groups do not live in exactly the same/geographical location.
## Footnote
Population - a group of organisms of the same species occupying a particular space at a particular time that can interbreed
166
Artifician selection increases the frequency of mutations. True or false?
False - artificial selection does not cause mutations.
167
How is the temperature tolerance of an enzyme changed when it is immobilised?
Increased
168
What are two disadvantages of using immobilised enzymes?
* The enzymes may become detached, mix with the product and need to be removed.
* Immobilisation can change the shape of the active site, reducing the rate of the reaction.
169
What is a pedigree analysis diagram?
Pedigree analysis diagrams show the inheritance of a particular phenotype over several generations.
170
If an allele is dominant, how would you be able to tell from a pedigree analysis diagram?
Someone with the dominant phenotype breeding with someone who doesn't have the phenotype produces offspring with the phenotype.
171
If an allele is recessive, how would you be able to tell from a pedigree analysis diagram?
An individual has the phenotype, even when their parents do not.
172
If an allele is dominant Y-linked, how would you be able to tell from a pedigree analysis diagram?
The phenotype is only found in males in the pedigree analysis diagram.
Fathers pass it on to their sons.
173
If an allele for a disease is dominant X-linked, how would you be able to tell from a pedigree analysis diagram?
Daughters inherit the X chromosome that causes the disease from their father.
Fathers pass it on to their daughters.
174
If an allele is recessive X-linked, what would the distribution of the phenotype be?
More males (females are more likely to get the recessive allele and a different one).
175
If an allele for a disease is recessive X-linked, how would you be able to tell from a pedigree analysis diagram?
Mothers pass it on to their sons, or fathers (with mothers) pass it on to their daughters.
176
In order to make enough tPA for medical use, geneticists take the gene coding for tPA and place it into a bacterium. The bacterium then produces tPA which is collected.
There are two possible methods for obtaining the tPA gene.
1. Use a restriction enzyme to cut out a DNA fragment containing the gene
2. Use reverse transcriptase to convert the mRNA coding for tPA into cDNA
Explain why the bacterium wouldn’t be able to make tPA using the DNA produced by method 1.
The DNA fragment produced in method 1 would **contain introns**. **Bacteria are unable to carry out splicing**, meaning that these introns would be present in the final mRNA strand. **Translation of this mRNA strand would result in a non-functional protein.**
177
Fatty acids are made up of a/an ____ that is attached to a/an ____.
hydrocarbon chain, carboxyl group
178
What is the common abbreviation for fatty acids?
RCOOH
179
Name the three structures that phospholipids can form in water.
micelle, phospholipid bilayer, **monolayer**
180
Bond between an -OH and H
Hydrophilic interaction
181
Bond between CH3 groups
Hydrophobic interaction
182
We current use the ____-kingdom system, made of:
six; Animalia, Plantae, Fungi, Protista, Archaea (Archaebacteria) and Bacteria (Eubacteria)
183
An insect trachea is supported by ____.
chitin
184
How does oxygen cross the tracheal fluid?
Oxygen **dissolves** into the tracheal fluid before **diffusing into the muscle tissue**.
185
Insects have what three body parts?
Head, **thorax**, abdomen.
186
A diploid cell has 64 chromosomes. How many chromosomes are in a nucleus which is undergoing telophase?
By telophase, the chromatids are now referred to as chromosomes, and each nucleus will have the same number of chromosomes as the original cell. So, there are 64 chromosomes.
187
What is meant by the term ''personalised medicine''?
Personalised medicine is a medicine that is tailored to **both the patient’s genes and the disease**.
188
What two things attract neutrophils to an infection site? What is this response to chemical stimuli called?
Chemicals released by pathogens, as well as **chemicals released by the body cells under attack** (e.g. histamine); **chemotaxis**
189
The pathogen releases chemicals that ____ pathogens ____ a concentration gradient.
attract, along
190
When the phagocyte reaches the pathogen, it binds to the pathogen via ____.
complementary receptors
191
During the cell-mediated response, a naive helper T cell binds to an antigen on an ____ or ____.
antigen-presenting phagocyte or B lymphocyte
192
During the secondary immune response, the memory B cell does what four things?
* **internalises the pathogen** (needs to bind to and recognise the pathogen first!)
* clones itself
* **binds to helper T cells**
* differentiates into plasma cells and memory B cells
193
What is the cell-mediated response and the humoral response?
Cell-mediated response - T cells
Humoral response - B cells
194
What are interleukins produced by, and what do they do?
Produced by helper T cell when it binds to processed antigen on APC.
Stimulates the B cell to clone itself
195
What four things can cloned helper T cells do?
* Stimulate phagocytosis.
* Stimulate killer T cells.
* Stimulate B cells to clone themselves (by releasing interleukins)
* Develop into T memory cells.
196
The dilution ratio is expressed as ____.
the volume of original solution transferred : total volume of new second solution.
i.e. 10cm^3 has 1cm^3 removed to 9cm^3 solution - 1:10
## Footnote
Dilution factor = RHS / LHS
197
Dilution factor equation
Dilution factor = final volume of solution / volume transferred
## Footnote
Dilution ratio = denominator : numerator
198
Multipotent stem cells are found in the bone marrow. What two cell types can they differentiate into?
Erythrocytes and neutrophils
199
Where in the plant is meristem found?
Meristem is found in the tips of shoots and roots and **between the xylem and phloem**.
200
Give three issues with using stem cells in scientific study.
**The collection of stem cells from embryos destroys the embryo.**
Some people have moral objections to this because they argue that embryos are living beings.
There is a risk that the patient’s immune system will reject the donated cells.
201
Are lipids polar? Describe how an observation you would know this from.
Lipids are generally nonpolar, hydrophobic molecules, meaning they do not mix with water.
202
What bond joins phospholipid heads and tails?
Ester bonds: These covalent bonds join the two fatty acid tails (hydrocarbon chains) to the glycerol backbone.
203
Lymph contains more/less protein that tissue fluid. Explain why.
More - antibodies are found in the lymphatic system (released in an infection).
204
Between 0C and 25C, the rate of photosynthesis less than/~/more than doubles.
Approximately doubles
205
The liver receives blood from the digestive system via the ____; this allows it to ____ that are absorbed into the blood in the small intestine.
hepatic portal vein, absorb and metabolise nutrients
206
In a liver lobule histology photomicrograph, what does a hepatic artery look like?
Small circular area of white (same colour as central vein) surrounded by a ring of hepatocytes
207
In a liver lobule histology photomicrograph, what does a hepatic portal vein look like?
Small, less circular area of white (same colour as central vein) surrounded by a ring of hepatocytes
208
In a liver lobule histology photomicrograph, what does a hepatic bile duct look like?
Very small, circular area of white (same colour as central vein) surrounded by a ring of darker stained cells
209
Describe the relatie sizes of the branches of hepatic arteries, portal veins and bile ducts.
Increasing size:
* Branch of bile duct
* Branch of hepatic artery
* Branch of hepatic portal vein
210
Suggest how an aquatic plant which absorbs shorter wavelengths of light can grow in deep water. [1 mark]
Shorter light wavelengths can penetrate greater depths of water.
211
Explain how a diuretic could help to reduce weight. [2 marks]
* Fewer aquaporins inserted into collecting duct plasma membranes
* More urine produced
* Rapid water loss
212
Furosemide is a diuretic which can be used as a masking agent, to hide the use of performance enhancing drugs. Suggest how it can be used as a masking agent. [1 mark]
Increased removal of drugs
Drugs are undetectable as more urine is produced (so drug concentration decreases)
213
Net pressure at the arterial end of a capillary is 1.3kPa. What would you expect the net pressure to be at venous end of a capillary?
~ **-**1.5kPa.
214
Where is ADH produced?
Hypothalamus
215
When and how is ADH released? (2/3)
Released by **exocytosis** when there are **action potentials** in **neurosecretory** cells
216
tropism
A **directional growth** response to a stimulus
217
At high exercise intensities, what is respired?
A mix of carbohydrates and lipids; not only carbohydrates (but mostly carbohydrates)
218
SOD converts superoxide ions to hydrogen peroxide and oxygen. Catalase converts hydrogen peroxide down. Explain why some cells may have high hydrogen peroxide concentrations. [2 marks]
* Catalase activity/concentration is too low.
* SOD activity is too high.
* Catalase gene may have a mutation.
219
Suggest how hydrogen peroxide might affect a cell's plasma membrane. [2 marks]
* Denatures membrane proteins
* Reacts with fatty acids/cholesterol/phospholipids
* Disrupts phospholipid bilayer
* Increases membrane permeability
220
Hormones like insulin and glucagon are contained in tissue fluid. True or false and why?
True - insulin and glucagon would need to enter tissue fluid to reach the receptors on the cells of the tissue
221
What enters the ornithine cycle?
Ammonia from deamination
222
ATP produced in respiration tends to be/not be used directly in photosynthesis.
not be
223
The COX enzyme produces molecules that stimulate inflammation. Aspirin is a drug that forms a covalent bond with the active site of the COX enzyme.
Which of the following terms best describes the action of aspirin?
Reversible/non-reversible inhibitor
Competitive/non-competitive inhibitor
Non-reversible (competitive) inhibitor
224
Explain why X-linked recessive disorders are less common in females than in males. [2 marks]
* Females have two X chromosomes / carry two alleles of the gene;
* (So) can be heterozygous
OR
* Recessive allele can be masked by dominant allele.
225
Describe the process of phagocytosis. [5 marks] (2 harder marking points)
* **Pathogen secretes chemicals** / chemotaxis;
* Receptors on phagocyte cell surface / plasma membrane recognise the chemicals/antigens on the pathogen’s surface;
* Phagosome;
* (Phagocyte) engulfs the pathogen and a vesicle is formed;
* Lysosomes and phagosomes fuse/phagolysosomes are formed;
* The digestion/hydrolysis of bacteria by lysozymes;
* **Soluble products from the breakdown are absorbed into the cytoplasm**/waste materials (antigens) are secreted/discharged
226
Lymphopenia is a disease in which your blood does not have enough lymphocytes. Patients with lymphopenia are often found to have an autoimmune condition.
Suggest why an autoimmune condition might give rise to lymphopenia. [3 marks]
* (An autoimmune condition means that) lymphocytes are attacking the body’s own cells
* (So) **cells that mature lymphocytes / lymphocytes themselves are destroyed**
* (So) reduces level/number of lymphocytes in the blood (leading to lymphopenia diagnosis)
* **Increases likelihood/probability of lymphocytes attacking body’s own cells;**
227
A scientist gives a group of patients a drug to see if it had a significant effect on the amount of lymphocytes produced. Give two issues with this method to make a conclusion.
No control group.
No statistical test done, so no, confidence level / probability of error calculated.
Not told if test is double blind or not.
228
Term for mutation that has no effect on the amino acid produced
Silent mutation
229
Most plants experience wilting if the soil in which they are growing becomes contaminated with salt.
Explain how osmosis is involved in the process of wilting. [4 marks]
* Salt lowers water potential of soil / water potential gradient is reduced
* Less water moves into roots by osmosis
AND any two from:
* **Water leaves vacuole**
* **Pressure forcing cell membrane against wall is lost**
* Cells become flaccid
* **Support of turgid cells** lost causing wilting
230
Sea Holly (*Eryngium maritimum*) is a halophyte which grows on dunes and sandy beaches. Despite the very low water potential of the soils in which they grow, these plants are able to absorb water through their root hairs.
Suggest and explain how this is possible. [3 marks]
* **Root hair cells store/contain high levels of ions/salts/solutes**
OR
* Ions/salts actively transported into root hair cells
* (So) water potential is lower inside the root hair cells than outside
* Water enters (by osmosis) down a water potential gradient
231
Two methods of isolation of gene from Bt
From bacterial chromosome using restriction endonucleases or using reverse transcriptase to generate cDNA from mRNa
232
Genetic engineering uses laboratory techniques to alter the DNA of an organism. This often involves the transfer of sections of DNA from one species into another.
A major insect pest of maize is the European corn borer moth (Ostrinia nubilalis). Its larvae cause plant collapse by eating the cells inside the stems causing them to weaken.
The bacterium *Bacillus thuringiensis* (Bt) is commonly used as a bacterial pesticide as it produces a toxin (Bt cry protein) which affects a wide range of insect pests.
In 1996 the first genetically modified maize producing Bt cry protein was approved for use in agriculture.
Describe the process which could be used to produce the genetically modified maize. [6 marks]
Vectors - use of a vector - plasmid from bacteria or Agrobacterium tumefaciens
**Possible use of marker genes to identify transformed cells**
Transfer of plasmid to maize stem cells - by using ***Agrobacterium tumefaciens*** to infect maize cells or **electrofusion? [latter stimulates cell division]**
**Propagation - reference to micropropagation - callus formation, use of hormones to promote differentiation, production of explants.**
233
A purified Bt toxin can be used as a pesticide spray. Field trials show that growing genetically modified (GM) maize gives better protection against damage by European corn borer moth larvae than spraying unmodified maize with Bt toxin.
Suggest an explanation for this finding. [1 mark]
In modified maize any cell damage caused by larvae releases toxin so all larvae are exposed.
OR
Spray may not penetrate stem or reach all parts of the plant
234
denitrification
conversion of nitrate into nitrogen gas/N2
235
What is ammonification carried out by?
Decomposers
236
Is denitrification anaerobic or aerobic?
Anaerobic.
237
Which bits of the nitrogen cycle are aerobic?
Nitrification, nitrogen fixation and ammonification (primarily aerobic)
238
Is ammonification anaerobic or aerobic?
Both, but *primarily* aerobic.
239
detritivore/detritus feeder
a type of heterotrophic decomposer that ingests and digests detritus e.g. earthworms. millipedes, flies
240
difference between detritivores and true decomposers
Detritivores must ingest detritus, whereas true decomposers secrete enzymes (externally) to allow them to consume nutrients
241
Three types of selection
Stabilising -> directional -> disruptive
242
What type of probe with a stain should be added after transfer of the bands to a membrane/paper?
DNA probes with a stain for DNA samples, RNA probes with a stain for RNA samples
243
What are proteins separated by in gel electrophoresis?
Proteins are separated by length and charge. Their length is determined by the size of their R groups and the number of amino acids present. Their charge is determined by their R groups.
244
How do pheromones defend plants against herbivores?
## Footnote
Pheromones trigger nearby plant leaves to produce more ____, which reinforces ____ (makes them ____) makes leaves harder to eat.
callose, cell walls, thicker
245
246
A standard growth curve for a population of bacteria of the same species in a closed system involves a death phase. Explain why there's a death phase. [2-3 marks?]
Reproduction stops/rate decreases rapidly due to exhaustion of resources / essential nutrients.
Build-up of toxic metabolic products means the death rate exceeds the reproduction rate.
247
Uses of DNA profiling (5)
Identifying genetic diseases
Identifying evolutionary relationships
Classifying organisms
As part of breeding programmes
Investigation of crime and paternity cases
248
The G1 and G2 checkpoints check for ____ and ____.
Cell size and DNA damage
249
State why root tissue is frequently chosen to study mitosis. [1 mark]
(Undifferentiated) cell*s* undergo mitosis **frequently**.
250
Identify one difference between prophase in mitosis and prophase 2 of meiosis. [1 mark]
Sister chromatids are not genetically identical (due to crossing over).
Chromosomes are already condensed in prophase 2 / meiosis.
251
Compare the plant **and** animal species that make up the climax and the pioneer communities. [6 marks]
Pioneer community:
Plants
* small species with example
* shorter life-cycle / fast growing
* seeds or spores
o large quantities produced
o can be **dispersed long distances**
o **germinate rapidly**
* self-pollinating / asexual reproduction
* able to **tolerate extreme environments** e.g. xerophytic / able to fix nitrogen
Animals
* few species (if any)
* mostly small species with example
Climax community
Plants
* more species than pioneer community
* larger species with example
* unable to tolerate extreme environments
* require **soil with ample water and minerals**
* **dominant species**
* slow growing
Animals
* larger species with example
* **more herbivore species**
* **carnivore species present**
* **longer food chains** (e.g. tertiary consumers)
252
A student investigates whether the species of tree in a forest affected the number of wood sorrel growing around it. Give two control variables they should consider. [2 marks]
Gradient of the ground at each tree.
Age / height / size of each tree.
Light direction at each tree.
Density of surrounding trees / shade from adjacent trees
(Time of day wouldn't affect the results.)
253
Chi-squared conclusion phrase
The **difference** between the observed and expected values is/isn't significant
254
Describe the role of T cells in the long-term immunity to a pathogen. [1 mark]
T memory cells can **rapidly produce T killer cells** if the pathogen returns (which can destroy infected cells).
255
Points to always make when talking about computational biology (4)
* Rapid processing and analysis use of **algorithms and statistical tests**
* **Prediction of amino acid sequences**
* Modelling of protein structure or **function**
* Use of **algorithms and statistical tests**
256
Points to always make when talking about bioinformatics (4)
* Facilitates **rapid information sharing** and retrieval
* Use of **algorithms and statistical tests**
* Large **data bases** of organisms' DNA sequences, amino acid sequences, protein structures and **metabolic pathways**
257
A scientist wants to identify which of two different species is the closest relative of a third species. They all come from different families. Explain why it is difficult for the scientist to come to a conclusion. [1 mark]
Further information is required (e.g. species' observable features, DNA base sequences) for classification.
258
Why do you use Taq polymerase in PCR?
Obained from thermophilic organisms so can withstand / not denature at higher temperatures.
It allows a **higher rate of DNA replication** than normal DNA polymerase (due to higher optimum temperature).
259
Describe what primers are. [2 marks]
Short pieces of DNA (1) that attach to bases at the start (and end) of the DNA fragment. (1)
260
What does PCR produce?
Double the number of DNA strands as before the process (produces identical double stranded DNA molecules).
261
Describe and explain how the polymerase chain reaction (PCR) is used to amplify DNA fragments. [6 marks]
* DNA is heated to **95°C**
* To break hydrogen bonds between the two DNA strands/denature the DNA;
* Temperature decreased to 55°C
* Which allows (forward and reverse) primers to bind to the ends of the **single stranded DNA**;
* (Finally,) temperature is increased to **72°C**/optimum temperature for Taq/DNA polymerase;
* Taq/DNA polymerase builds complementary strands of DNA/adds complementary nucleotides;
* To produce new **identical double stranded DNA molecules**
* **Process is repeated**/cycled several times (to amplify the original DNA fragment). -> whole point of Taq polymerase
## Footnote
Note: must include the final marking point for 6 marks.
262
Describe and explain how primers are used in the polymerase chain reaction. [4 marks]
* (Primers are) short pieces of DNA
* Attach / bind / anneal to bases at start (of DNA fragment)
* (Primers are) **complementary**
* **Allow DNA polymerase to attach**, which adds nucleotides
* **Prevent (DNA) strands rejoining**
263
What disappears in prophase? (2)
**Nucleolus**, nuclear envelope breaks down
264
What begins to form in prophase?
Spindle fibres
265
Suggest why wild wheat varieties are important for breeding a new variety of wheat that is resistant to wheat rust. [2 marks]
There is genetic variation in the wild varieties,
which could include wheat rust-resistant genes.
266
Suggest how stabilising selection for number of eggs laid occurs. [3 marks]
Variation in number of eggs laid due to mutation.
Middle clutch size is favoured because it increases chance of survival of offspring.
Offspring reproduce and pass on genes.
267
Explain what allopatric speciation is caused by. (1)
Geographical isolation
268
Phenotypic variation due to genetic factors is inherited, while phenotypic variation due to environmental factors is not. Explain why. [1 mark]
Genetic factors affect the **DNA of gametes** whereas environmental factors do not. (1)
[whereas environmental factors affect DNA of somatic cells]
269
Explain why bacterial population growth is slow initially. [1 mark]
It takes **time** for the bacterial cells to divide.
270
P. maculosa population when grown with P. oris increases rapidly then decreases towards 0. P. oris population contunues to increase rapidly.
Suggest why there is a difference in the final population size of P. maculosa when grown with P. oris compared to when it is grown alone. [2 marks]
**Unsuccessful** interspecific competition for food sources / more of the food source is taken by P. oris;
P. oris **outcompetes** P. maculosa.
271
Name the process in which a plasmid is added to a host cell.
Transformation
272
Give four benefits of using a fluorescent marker gene over an antibiotic resistance marker gene.
* Fluorescence is an observable property.
* There is **no risk of antibiotic resistance being passed on** to other bacteria.
* **Fluorescence marker genes are more economical.**
* The test to identify which bacteria contain the recombinant bacteria doesn’t involve killing them.
273
A grasshopper is enclosed with soda lime in a test tube connected to a manometer. The other end of the manometer is connected to a second empty, bunged test tube.
In which direction would the liquid travel for a cricket, with a higher RQ than the grasshopper, travel?
A higher respiratory quotient means that the cricket requires **less oxygen for respiration** than the grasshopper. [RQ = CO2 produced / O2 consumed]
This means the **volume of air in the tube decreases less** with the cricket, so the coloured liquid moves **less far to the left**.
274
Estimate the diameter of a bacterial cell.
0.1 - 10 micrometres
275
Describe two improvements to a serial dilution method, other than using different equipment, that could improve the accuracy of a bacterial population estimate from a plated and incubated petri dish. [2 marks]
* **mix** (each dilution)
* **replace (micro)pipette tips between each transfer**
* repeat the plating (at least three times) and calculate a mean [not whole serial dilution[
* **take photo of final plate** so colonies can be counted
* reduce the number of, dilutions / transfers (to reduce random error)
276
Explain why using a frame quadrat compared to a point quadrat is better. (4) [1 mark]
* **Easier to measure tall plants**/bushes
* Less likely to **harm small animals**
* More representative
* Less likely to **miss** (rare) species
277
Without changing the actual method of sampling, explain one way to improve the results. [2 marks]
* Measure on different days of the year/seasons
* Less likely to miss species
OR
* Different species grow at different times of the year
278
State and explain one safety precaution that students should take when dissecting vascular tissue. [2 marks]
**cut away from the body**
OR
idea that only one person at a time should work on the specimen
OR
use sharp, scalpel / scissors / knife / razor blade
*Explanation:* to avoid cuts
wash specimen / **wash hands** / wear gloves
*Explanation:* to avoid **infection** (with plant pathogens) / allergic reaction
279
How do you control the temperature of a potometer?
e.g. use of a climate-controlled room,
thermostatically controlled chamber
## Footnote
Note: a water bath is not appropriate in this
experiment
280
Explain how curled leaves limit water loss. [1 mark]
Decreases the surface area exposed for transpiration
281
Explain how thick waxy cuticles limit water loss. [1 mark]
They are impermeable to water / stop water vapour from escaping the leaf.
282
State how H+ are transported between the inside and outside of thylakoids.
**Pumped / moved** [not active transport due to ETC] into thylakoids.
283
If an experiment has lots of limtations, the conclusions draw are ____.
What causes these limitations?
limited
Few control variables
Small sample sizes
Assumptions
Lack of statistical analysis
284
State what you may be able to identify from a photomicrograph of pancreatic tissue.
Islet of Langerhands
Acini
Blood vessels
(Branch of pancreatic) **ducts**
285
Outline how a gardener could produce many cloned plants from a bulb. [1 mark]
**split / divide / cut** bulb and plant / repot
286
What happens to the runner when a shoot grows? [1 mark]
The runner between the two plant(let)s dies.
287
cambium
A plant tissue with stem cells between the xylen and phloem from which phloem or xylem grows by cell division
288
Suggest a limitation of using a permeability experiment, where an antibiotic is bound to a fluorescent label and the fluorescence intensity is measured, to predict antibiotic effectiveness. [1 mark]
Bacteria may have (other) methods of resistance (e.g. efflux pumps / altered target / deactivating enzymes) / antibiotic may not be effective inside cells;
OR
Fluorescent label may change the permeability of the bacterial membrane to tetracycline.
289
loop of Henle function
Enables high concentration of ions in the medulla / maintains balance of water and ions in the blood
290
Bowman's capsule adaptations and explanations. (2) [4 marks]
Basement membrane
- Has small gaps/pores/fenestrations which prevent larger molecules from entering the kidney.
Podocytes
- Have a large surface area due to many projections to allow small molecules to pass through.
A Level Biology
flashcards
Decks in class (15)
# Cards
-
Module 2 Section 1 - Cell Structure95
-
Module 2 Section 2 - Biological Molecules171
-
Module 2 Section 3 - Nucleic Acids75
-
Module 2 Section 4 - Enzymes58
-
Module 2 Section 5 - Biological Membranes113
-
Module 2 Section 6 - Cell Division101
-
Module 3 Section 1 - Exchange and Transport72
-
Module 3 Section 2 - Animal Circulatory System23
-
Module 4 Section 2 - Biodiversity65
-
Module 4 Section 3 - Classification and Evolution90
-
Module 5 Section 1 - Communication and Homeostasis12
-
Module 5 Section 2 - Excretion23
-
Module 5 Section 5 - Photosynthesis1
-
General Bio Knowledge & Science Skills for Exams42
-
Specific Struggles290
