U1T6 - Continuity of Cells Flashcards Preview

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Flashcards in U1T6 - Continuity of Cells Deck (50)
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1
Q

How do most living organisms grow?

A

By increasing the number of cells they have. Cells divide.

2
Q

What are 2 types of cell division?

A

Mitosis + meiosis.

3
Q

What are the 3 main stages of the cell cycle?

A

Interphase (G1, S, G2), Mitosis/meiosis (Nuclear division) + Cytokinesis (Cell division)

4
Q

What happens to the nucleus during interphase?

A

Nucleus appears to be resting, Chromatin is dispersed throughout. Metabolic processes take place to prepare cell for its metabolic role + cell division.

5
Q

What happens during interphase?

A

Amount of DNA in nucleus doubles (New DNA synthesised + histone proteins made) new organelles made (Mitochondria), ATP store built up for nuclear division + spindle proteins synthesised.

6
Q

What are the 3 growth phases of interphase?

A

G1 phase, S phase + G2 phase.

7
Q

What is the purpose of the 2 gap phases?

A

Give cell time to monitor internal + external environment to ensure all is ready for S Phase + Mitosis/meiosis. Cell can delay progress through G1 and go to G0 in unfavourable conditions.

8
Q

Describe the checkpoints which exist within the cell cycle.

A

If growth phases haven’t been carried out properly, checkpoint stops cell dividing so cell is destroyed. Some genes code for these, one is a growth factor receptor which is on the cell surface membrane + once the growth factor is present, the cell can detect it and it can proceed.

9
Q

What happens during mitosis?

A

Chromosomes present as chromatids which were formed during interphase are separately + distributed to 2 daughter nuclei.

10
Q

What are the 4 phases of mitosis?

A

Prophase, metaphase, anaphase + telophase.

11
Q

What happens in animal cells during prophase (Mitosis)?

A

Centrioles divide + move to opposite ends (poles) of cell. Protein microtubules develop from each centriole, forming spindle fibres, some of which extend from pole to pole. Towards end of prophase, each chromosome exists as 2 chromatids held together by centromere. Nucleolus disappears + nuclear membrane breaks down so chromatid pairs are free in cytoplasm.

12
Q

What is the difference in prophase in plant + animal cells (Mitosis)?

A

In plant cells, there are no centrioles so the spindle forms independently.

13
Q

Describe the process of cytokinesis in animal cells.

A

Cleavage furrow forms as cell surface membrane invaginates + cell splits into 2.

14
Q

Describe the process of cytokinesis in plant cells.

A

Cell plate laid down along cell centre which eventually becomes cell wall (Middle lamella + primary cell wall) Golgi apparatus synthesis materials needed for new cell wall.

15
Q

Give an example of a mitotic poison + its use.

A

Vincristine which inhibits mitosis/cell division.

16
Q

Why are mitotic inhibitors used in cancer treatments?

A

Cancer cells can metastasize through continuous mitotic division. This interrupts cell division as 2 sets of fully formed chromosomes are supposed to separate into daughter cells.

17
Q

What do antimetabolites do?

A

Induce dell death during S phase of cell cycle when they’re incorporated into RNA/DNA or inhibit enzymes needed for nucleic acid production.

18
Q

Give an example of an antimetabolite + its use.

A

Uracil is pyrimidine nitrogenous base using in nucleic acid synthesis. 5’Fluorouracil prevents DNA synthesis during S phase of cell cycle.

19
Q

How are chromosomes organised?

A

Contain 1 long single molecule of DNA. 46 chromosomes in human cell so 46 individual DNA molecules, each being 4m long. To prevent entanglement in nucleus, DNA are coiled around histones.

20
Q

What is a human karyotype like?

A

All chromosomes from each pair are similar in size, except for sex chromosomes.

21
Q

What would happen if a diploid sperm fertilised a diploid egg?

A

There would be 46 pairs of chromosomes in the fertilised egg - double the normal number.

22
Q

Why do we have inherited characteristics?

A

Zygotes divide by mitosis producing diploid cells with identical chromosomes which carry the same genes as those in the zygote, this is why we have inherited characteristics.

23
Q

What is meiosis for, where does it take place, what does it result in, where are the gametes made?

A

Sexual reproduction + genetic variation, reproductive organs (Ovaries + testes), 4 haploid gametes which aren’t genetically identical by dividing twice, testes + ovaries in humans or anthers + ovules in plants.

24
Q

In a chromosome, is a gene on the dark or light band?

A

The dark band.

25
Q

What happens during meiosis interphase?

A

DNA content of cell doubles + new cell organelles are formed.

26
Q

What does the 2 chromosomes in each bivalent being pulled apart during anaphase 1 ensure?

A

One chromosome from each homologous pair ends up in a daughter cell.

27
Q

What does cytokinesis produce at end of Meiosis 1?

A

2 daughter cells (1st division) with haploid number of chromosomes. Number of chromosomes in each cell has been halved at end of meiosis 1.

28
Q

What is the main goal for meiosis? What does this depend on?

A

For a gamete to contain one of the chromosomes from a homologous pair. Chromosome in gamete depends on how chromosomes line up on the equator at metaphase 1.

29
Q

What is independent assortment important for?

A

Genetic variation in the next generation.

30
Q

How many chromosomes do humans have?

A

23 pairs.

31
Q

Before crossing over, what is the state of the chromatids of each chromosome?

A

They are identical, possessing the same genes + alleles.

32
Q

At the G1 checkpoint, what must be ensured about the cell?

A

Cell has reached a critical size, enough nutrients available for next stage, necessary growth factors in place + no DNA damage.

33
Q

G0: Lymphocytes

A

Many lymphocytes are in G0. They only move out of this state if triggered to do so by presence of specific antigens.

34
Q

Describe the G2 checkpoint.

A

At end of G2 phase, cell checks that DNA replication has taken place accurately + no DNA damage.

35
Q

What happens at the metaphase checkpoint?

A

Cell checks that all chromosomes have properly attached to spindle fibres.

36
Q

What are the main differences between mitosis and meiosis?

A

Meiosis only takes place in reproductive organs, involves 2 divisions creating 4 daughter cells + chromosome arrangements in daughter cells are both different from each other + the parent cell.

37
Q

What happens to cells from the primary tumour?

A

Shed + carried around body by circulatory system, producing a secondary tumour. (metastases)

38
Q

What is DNA unzipping inhibited by?

A

Drugs adriamycin + cytoxan. If 2 DNA strands can’t be exposed then DNA replication can’t take place.

39
Q

What happens if there’s a faulty checkpoint?

A

Certain gene mutations can cause a faulty
receptor to be produced, which is always in the ‘on’
state, whether the growth factor is present or not.
The cell repeatedly goes through the whole cell
cycle, dividing continuously.

40
Q

Describe how vincristine works.

A

It interferes with mitosis in rapidly dividing cells. It binds
to tubulin, which forms the microtubules of the spindle. When vincristine is bound to tubulin, the microtubules cannot be formed + so anaphase can’t take place. Chromatids therefore cannot be pulled apart. It is a mitotic poison. Can affect rapidly dividing
epithelium in intestine + bone marrow.

41
Q

Describe how 5’flouracil works.

A

Inhibitor of enzyme necessary for DNA replication. Interferes with nucleotide production carrying thymine so few nucleotides are available. DNA replication can’t be completed when it’s present so is an ‘antimetabolite’.

42
Q

How many chromosomes in a gamete?

A

22 autosomes + 1 sex chromosome.

43
Q

What are 2 methods of genetic shuffling used in meiosis?

A

Crossing over during prophase 1 + independent assortment during metaphase 1,

44
Q

What is the difference between metaphase in meiosis and mitosis?

A

In meiosis, they line up in bivalents + chromatids are not separated.

45
Q

Explain how mitotic poisons contribute to the treatment of cancer.

A

They stop mitosis occurring successfully/fully and so the tumour cells cannot divide.

46
Q

What happens during the G1 checkpoint?

A

Checks for DNA damage, cell size, availability of nutrients + presence of growth factors.

47
Q

What happens during the G2 checkpoint?

A

DNA replication + cell size.

48
Q

What are centrioles?

A

The paired structures from which spindle fibres originate in animal cells.

49
Q

What is the behaviour of chromosomes from prophase 1 to prophase 2?

A

Chromosomes are in homologous pairs, they exchange gene during crossing over at chiasmata and line up along cell equator in recombinant pairs. Spindle fibres attach to centromere and chromosomes separate before a new nuclear envelope is formed.

50
Q

How do chiasmata result in genetic variation?

A

They are the part where 2 chromatids join together and exchange DNA sections during crossing over and form recombinant chromosomes.