Molecular Evolution Flashcards
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 can reproduce in its environment
What is the modern synthesis?
Evolution can be unified with genetics to explain molecular processes underlying evolution
What is the main source of heritable changes in a species?
Genetic variation
What are the four things that affect frequency of genetic variants?
Selection, mutation, migration and genetic drift
How does selection affect the frequency of genetic variants?
Variants that give a positive advantage will be selected for, however some vital genome sequences are conserved
How does mutation affect the frequency of genetic variants?
The process by which variation in the genome arises
What do mutation frequencies depend on?
Selection and when they first arose
What is it called when migration affects the frequency of genetic variants?
Admixture
What does admixture mean?
The movement of people from a different population results in new pools of variants being introduced into an existing population
How does genetic drift affect the frequency of genetic variants?
The frequency of variants changing due to chance - not all variations will be passed on
Why does sequence conservation happen?
To stop vital proteins being lost
Where is there high conservation?
Coding regions
Where is there intermediate conservation?
Promoter, 5’UTR, 3’UTR and terminator regions
Where is there low conservation?
Introns, 3rd codon base and parts of the terminator region
What is sequence conservation used for?
Cross species comparison and conservation
Why is cross species comparison important?
To generate an evolutionary profile for a gene or gene family
Why is cross species conservation important?
Allows us to identify important gene regions and allows us to concentrate on areas that are important in novel genes
What is the main aim of a phylogenetic tree?
To illustrate the relatedness of different species/ strains/ sequences
What determines the distance between two things on a phylogenetic tree?
How similar they are
How is time estimated on a phylogenetic tree?
By measuring mutation rates
What is gene duplication generally caused by?
Unequal crossing over during meiosis
What happens to the genes after gene duplication has taken place?
One continues the original function, but the other evolves new functions through changes in the coding and/or control sequences
What is unequal crossing over?
Recombination between sequences that are not the correct sequence but are very similar
What are the two clusters of globin genes?
Alpha-like and beta-like
Where are the alpha-like globin clusters found and what are they made up of?
Chromosome 16 - 3 genes and 3 pseudogenes
Where are the beta-like globin clusters found and what are they made up of?
Chromosome 11 - 5 genes and 1 pseudogene
What are the genes on the globin gene clusters arranged in order of?
Expression during development
What has divergence of promoters allowed on the globin gene clusters?
They bind different transcription factors and allow the expression of genes at different stages of development
What are pseudogenes?
Non-functioning genes that look similar to functioning genes
How do pseudogenes come about?
Through many mutations
When does sickle cell anaemia normally present?
5-6 months of age
What are the main symptoms of sickle cell disease?
Anaemia, acute pain episodes, increased infection frequency
What are the less common symptoms of sickle cell disease?
Stroke Pulmonary hypertension Gallstones Liver and kidney problems Joint problems Delayed puberty
What causes sickle cell anaemia?
A single base substitution in the beta globin gene from GAG -> GTG
Where does the substitution for sickle cell anaemia take place and what amino acids change?
Position 7 of the protein- glutamine -> valine
What type of genetic disease is sickle cell disease?
Autosomal recessive
Where is sickle cell disease common?
African, Mediterranean, Middle Eastern and Indian populations
Why is sickle cell disease still common in some parts of the world?
One HbS variant confers resistance to severe malaria
