Molecular Evolution Flashcards
What does the theory of “On the Origin of Species “ explain?
It explain the current variety of life on earth
What are the 2 main concepts the charles darwins theory?
Natural selection and Fitness
What is natural selection?
The effects of a wide range of factors on the frequency of heritable changes in a species
What is fitness?
How well a species is able to reproduce in an environment
what happens if the fitness increase ?
This change will be selected for
What happens if the fitness decreases?
The change will be selected against
What is the Modern Synthesis?
Genetics alongside evolution can be unifies to explain the molecular processes underlying evolution
What is the main source of heritable changes in a species?
Genetic Variation
What effects the frequencies of genetic variants? ( 4 in total)
Selection
Mutation
Migration
Genetic Drift
What is Selection?
Selection is where genetic variants display a positive advantage that will be selected for and passed on to further generations
Give examples of Selection
- resistance to a disease
- ability to metabolise a new food source
- antibiotic resistance
- changes in appearance that enhances mating choice
In terms of the genome, what does it mean to be conserved?
Parts of the genome that are resistant to change
Why are some parts of the genome conserved?
They are conserved as they contain vital sequences and are essential for the organisms survival
What is Mutation?
The name of the process that allows variation to arise in the genome
What does the number of mutations depend on?
It depends on the selection and when the first mutation arose
How may a variant be rare?
It may be rare if it recently arose or if it is deleterious
or both!
What is Migration?
Physical movement of people form a different population resulting in new pools of variant being introduced to the existing population
What is another term used for migration ?
Admixture
A population frequency may change due to what?
It can change due to Admixture
not just due to disease
What is Genetic Drift?
How the frequency of a variant changes in a population due to chance
What mechanism will result in not all genetic variants being passed on?
Recombination
True or False
Will all organisms pass on all their genetic variants
FALSE
- not all organisms will pass on their genetic variants
- all variants are subject to genetic drift
What type of sequences don’t show evidence of variation?
DNA sequences that are vital to the survival of the organism
What happens if there is variation in conserved regions? and why?
they are usually selected against as they are likely to have deleterious effects
Which regions have high conservation ?
Coding regions
Not exons - as these contain non -coding regions
Which regions have intermediate conservation?
Promoter
5’ UTR
3’ UTR
Terminator
Which regions have low conservation?
Introns
3rd Base of codons
terminator
Why is there flexibility in variation of the 3rd base of a codon?
Due to some amino acids having multiple codons coding for it
What can a cross species comparison be used for?
Used to generate an evolutionary profile for a gene or a gene family
Give an example of a conservation gene
NAMPT
Nicotinamide Phosphoribosyltransferase
What are Phylogenetics?
Phylogenetics is the study of the history of our genome
What is the pattern for studying phylogenetics
- observe sequences
- reconstruct evolutionary histories
- learn more about evolutionary processes
- develop better evolutionary models
- repeat
What is the main aim of a phylogenetic tree?
To illustrate the relatedness of different species
What does distance on a phylogenetic tree mean?
Distance between two entities shows how similar they are
What is the distance on the tree due to?
Distance is due to evolutionary pressures and times
How is time estimated?
Time is estimated by mutation rates
What is the theory of how HIV was introduced?
HIV was introduced via a contaminated polio vaccine
How did the polio vaccine come to be contaminated?
Polio vaccines were made via cultured chimpanzee cells which may been infected with SIV
What is Gene duplication?
The duplication of a DNA sequence containing a gene
What is the mechanism behind Gene Duplication?
The unequal crossing over during meiosis
What happens to the copies after duplication?
- One copy will continue with the original function
- The other copy can evolve to have a new function due to changed in the coding sequence
What are the two clusters of Globin genes?
- Alpha like
2. Beta like
Which chromosome is Alpha like globin genes found on? what type of genes make up this cluster?
Chromosome 16
4 genes and 3 pseudogenes
Which chromosome is Beta like globin genes found on? What type of genes make up this cluster?
Chromosome 11
5 genes and 1 pseudogene
Through what mechanisms have globin genes evolved from?
Through duplication and accumulation of mutations (divergence)
What are pseudogenes?
Non functioning genes
What does divergence of promoter allow?
Allows different transcription factors to bind meaning the expression of genes at different stages of development
eg. embryo -> foetus -> postnatal
TRUE OR FALSE
pseudogenes have many mutations and are non functional
True
there are many pseudogenes in our genome
What processes do pseudogenes complicate?
PCR and sequencing
What causes sickle cell disease?
Single nucleotide mutation
When do symptoms of SCD usually show?
5-6 months of age
What are the main symptoms?
- Anaemia : fatigue, restlessness, jaundice
- Acute Pain Episode : due to o2 deprivation in tissues
- Increase frequency of infections : spleen damage
Where does the single base change occur for SCD?
In the Beta Globin gene of Haemoglobin A
What is the new mutated Haemoglobin known as?
Haemoglobin S (HbS)
What is the codon change for SCD?
GAG to GTG
The codon changes what amino acid in to what? at what position?
Glu to Val at position 7
What type of disease is SCD?
Autosomal Recessive disease
What is the effect of having two copies of the HbS variant?
It has a negative effect on reproductive ability
What is the effect of only having one copy of the HbS variant?
Resistant to Malaria
What is meant by ‘Heterozygous Adavantage’
It means the HbS variant is maintained in the population when otherwise it would have been selected against and lost
When did the SCD mutation arise?
approx. 7300 years ago
