W1-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 is able to reproduce in its environment. Anything that increases fitness is selected for, anything that decreases fitness is selected against and other neutral changes will vary randomly.
What is the modern synthesis?
It was realised that evolution could be unified with genetics to explain the molecular process underlying evolution. Genetic variation is the main source of heritable changes in a species.
What are the frequencies of genetic variance affected by?
Selection, mutation, migration, genetic drift
What is selection?
Genetic variants with positive advantages will be selected. Eg, resistance to disease, attractiveness. Some parts of genome are conserved - contains vital sequences.
What is mutation?
Name for the process where variation in genome arises from mutations. We all have a lot of variants - frequency will depend on selection and when they first arose.
A rare variant may have arisen recently or be deleterious and being selected against/both…
What is migration?
Physical movement of people from a different population to an existing one. This is admixture. Population frequencies can change purely due to admixture- not disease related.
What is genetic drift?
Frequency of a variant changes in a population due to chance. Not everyone passes on their genes. Mechanisms like recombination means not all variants are passed down. All variants are subject to genetic drift.
What is meant by sequence conservation?
DNA sequence vital to survive doesn’t usually show much variation. Most variants are likely to be deleterious. Some flexibility in the third base since some are degenerate.
High conservation = Coding regions
Intermediate conservation = Promoter, 5’ untranslated region, 3’ UTR terminator
Low conservation = Introns, 3rd base of codons, terminator.
What can you use sequence conservation for?
Cross-species comparisons to make evolutionary profile for gene/gene family.
Cross-species conservation allows identification of the important region of a gene (and its protein)
Allows us to concentrate on areas that appear to be important in novel genes.
What is a Phylogenetic tree?
Shows relatedness of different species/strains/sequences. Distance between 2 entities on a tree = related to how similar they are. Distance is normally related to both evolutionary pressures and time. Time is estimated by measuring mutation rates.
What are infectious diseases that could be determined with phylogenetics?
- Theorised that HIV had been introduced to some human populations through contaminated polio vaccine in Africa.
- Some polio vaccines used to be produced by using cultured chimpanzee cells - could have been infected with SIV.
What is Gene Duplication?
Duplication of a DNA sequence containing a gene. The typical mechanism is unequal crossing over during meiosis. After duplication, one copy can continue the original function. Other copy can evolve new functions through changes in the coding sequence and/or control sequences.
What is unequal crossing over?
Re-combination between sequences that are not the correct sequence but are very similar. Often low copy numbers repeat sequences.
What are globin genes made of?
Alpha-like
Beta-like
Genes are arranged in order of expression during development. The cluster contains three functional genes (α1, α2, and ζ2), three pseudogenes
