What is the RNA world hypothesis?
Early life thought to be based on self-replicating, self catalytic, RNA molecules
What are opsins?
G protein coupled receptors that convert light to nerve impulses
What are hCONDELs?
Regions of deletions in human genomes that are highly conserved in closely related relatives
How did eukaryotes arise?
Through endosymbiosis
How can phylogenetic relationships be represented?
Using phylogenetic tree diagrams
What is radiometric dating?
Measuring the ratio of parent daughter nuclides
Outline the order of appearance of cells in the fossil record
Prokaryotes -> Eukaryotes -> Multicellular organisms -> Animals
Define classification
Arranging taxa into an ordered, heirarchal system
What is the start codon present in bacteria?
A modified version called Formyl-methionine
Give examples of analogical structures
Insect wings and Bird wings
- different developmental mechanisms
- but have overlapping molecular components
Name the PAX6 homologs
Mouse - small eye
Drosophilia fly - eyeless
Humans - PAX6 aniridia
Why is the rate of radioactive decay constant?
It is not affected by the following factors
- temperature
- pressure
- chemicals
- electrical fields
- magnetic field
What can be determined using the fossil record?
The order and age of organisms
Give an example of analogical molecules
Crystallins (lens proteins)
many different transparent proteins in different species
all have different functions as well
provide stability, transparency and refraction
How has the diversity of cells increased so much?
The rate of diversification increases with multicellularity
What is molecular analogy?
Molecular evolution convergence
- proteins can have similar functions with no common molecular structure
How has the plastid genome evolved?
Has a loss of genes compared to its earlier form
The ‘lost’ genes are present in the nuclear genome
What are the 4 basic processes of multicellularity?
- spatial organisation
- change in form/ specialisation
- growth
- differentiation
How can mutations increase survival?
If mutation results in beneficial characteristics, the organism will survive better than its competition
What is the fossil record?
Rock and organic material dated by measuring decay of natural occurring radioactive isotopes
Approximately how many times has the cellular structure of eyes evolved?
Over 40 times - origin of eye components varies
What is a homeodomain?
Transcription Factors found in genes regulating morphogenesis in plants, animals and fungi
Give an example of a mutation tolerated by DNA
Sickle Cell Anemia (ScA)
- mutation in both β globin gene Glu6Val
- mutant Hb molecules aggregate and form crystals when deoxygenated
- results in cells with sickle shape
- cells get trapped in capillaries -> can cause tissue death
What do all bacteria, archae and eukaryotes have in common?
They all carry genetic material DNA
What is the function of the Drosophilia eyeless / PAX6 gene
Pax6/eyeless is involved in development of eyes & brain of both invertebrates & vertebrates
How do eukaryotes detect light?
Via Opsins
What are the consequences of gene duplication in evolution?
- Complementary functions (original and duplicated genes carry out same function)
- non overlapping functions
- Regulatory mutations partition the activity of ancestral genes
What are orthologs?
two genes from different organisms that have arisen from a common ancestor
What is the start codon used in archae & eukaryotes?
Methionine AUG
Why is radiometric dating an accurate way to determine age?
Parent and daughter nuclides cannot leave or enter materials once they have formed
There is no intrusion of other, later rock
No contamination
Describe and explain the presence of HOX genes in vertebrates today
Vertebrates have 4 HOX gene clusters
- 2 duplications of ancestral chromosome
Gene order along chromosome corresponds to position of expression within the embryo
determined by homeodomains
What allows for diversification?
Gene duplication
Where are catalytic enzymes found?
Ribozymes are present in organisms from bacteria to humans
How do different flu strains evolve?
Flu strains infecting the same cell can swap parts of their genetic material
Why do bacteria normally not grow in citrate?
Under normal conditions With oxygen
Promoter for citrate is OFF
bacteria don’t produce enzyme
so don’t grow in citrate
What is the function of the plastid genome?
Encode the proteins necessary for plastid function
What is meant by homology?
Two structures that are from a common ancestral version
How can phylogenetic relationships be studied?
The fossil record
Molecular analysis
What is The Cambrian Explosion?
The sudden appearance of complex organisms in the fossil records
What is the major difference in modern eukaryotes compared to their earlier form?
Modern eukaryotes contain plastids - mitochondria and chloroplasts
Why are some mutations in DNA tolerated?
mutations are tolerated based on their effect - can sometimes have an advantage
How are morphological differences established in cells?
During development even though reproductive, selective pressure acts on the adult form
What is the advantage of the gene mutation causing sickle cell anemia?
Mutation of 1 β globin gene can give protection against malaria due to lower parasitaemia
-fewer complications -> improved malaria survival rates
Describe the genome of present day eukaryotic opsins
Eukaryotic opsins share sequence homology
Diverged to detect different wavelengths of light
What is catalytic RNA?
Ribozymes
Which animals is the HOX gene present in?
In vertebrates (chromosomal organisation and function is conserved)
How are animals so different despite evolving from the same genome?
Animals share the vast majority of their genes.
Their gene sequencing is the same but the gene expression differs
Give an example of homological structures in organisms
Tetrapod limbs
- have similar developmental mechanisms
What is meant by the term phylogenetics ?
New species arise from earlier species sharing relationships
What are the 2 types of molecular homology?
- Paralogs
- Orthologs
How did bacteria and archae come about?
Overtime DNA and proteins became surrounded by phospholipids
Outline an experiment that can be used to observe the process of evolution
- Grow 12 colonies of E. coli on petri dishes
- Every day take each culture and place in a clean flask
- Every 500 generations (75 days) freeze samples
4 Test for ability to grow in citrate in the presence of oxygen
Explain the function of N-neuraminidase gene in flu strains
An enzyme which allows viral particles to be released from the cell
- the better the cell is at releasing, the further the virus can spread
How can mutations act as molecular clocks?
Species that share a recent common ancestor will have fewer differences/mutations than species
more distantly related
Describe the evolutionary structure of HOX genes
- Paralogs (duplicated from ancestral animals)
- Present in clusters along chromosome
Approximately how many hCONDELs have been identified in the human genome?
583 regions identified across all chromosomes
Which parent are mitochondria inherited from?
Mitochondria are maternally inherited
Define evolution
New species arise from earlier species via an ongoing process driven by accumulated, heritable
changes
What is the consequence of mutations in the PAX6 homologs?
Lead to retinal defects and ectopic eyes
Define what is meant by analogy?
Similar structures with no common ancestors but have similar functions due to convergent evolution
(through selection ended up with similar functions)
How are living organisms classified?
Based on morphological or molecular criteria
Define the term taxonomy
The naming of groups of organisms
What are paralogs?
two genes from the same organism arisen by duplication
What happens if duplicated genes mutate?
Function differs slightly to original gene
organism still survives as original genes till present
What evidence is there to support the theory of endosymbiosis?
- Mitochondria have their own circular genome
- MtDNA replicates independently of nuclear DNA
- Mitochondria formed by fission of existing mt
- mt genome share similarities with typhus bacterium ricketta prowazeki
How do changes in genotype arise?
- mutation
- recombination of genetic material
- natural selection
- genetic drift
- gene flow
- applied selection
What is meant by the term morphogenesis?
Anatomical development
Explain what the term Phylogeny means
The determination of ancestral relationships of organisms and their evolutionary history
Which genes are swapped amongst flu strains?
H-haemagglutinin (binds)
N-neuraminidase (release)
How do bacteria evolve to grow in citrate in presence of oxygen?
The citrate gene is adjacent to Rnk promoter
RNK Promoter is always ON in presence of oxygen
some bacteria are able to grow in citrate
they duplicate DNA segement containing citrate, RNK promoter and RNK
Duplication results in the citrate gene to be turned on in oxygen presence
What is the earliest cell type?
Prokaryotes
How does H-haemagglutinin work?
Binds host cells by recongising specific receptor sites on their cell surface and infects
What is the function of homeodomains?
Homeodomains share a characteristic protein fold structure that binds DNA
What are HOX genes?
Homeotic genes that control the body plan of an embryo along the head-tail axis
Why did the RNA world evolve into DNA genomes?
DNA is more stable than RNA
- greater range of protein enzymes