Molecular Evolution

Question 1

What is relative fitness (W)?

Answer 1

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 changed will vary randomly

The average number of surviving progeny of a genotype (compared with competing genotypes) after one generation

Question 2

What does W<1 mean for the allele frequency?

Answer 2

If w < 1, the frequency of the allele
- will decrease with each generation

• until the allele disappears (negative selection)

Question 3

What does a W > 1 mean?

Answer 3

If w > 1 the frequency of the allele
- will increase with each generation

• until the allele reaches fixation (positive selection)

Question 4

How can we use molecular phylogeny to identify ancestors of species?

Answer 4

DNA mutations accumulate over time, so species that share a recent common ancestor will have fewer differences than species that are more distantly related

Question 5

How do we create a phylogenic family tree?

Answer 5

using sequence data - utilise conservation

Question 6

What are the medical implications of phylogenic trees?

Answer 6

find antibiotics

substances produced by fungi, which are toxic to bacteria, but not fungi, able to be identified - antibiotics

Question 7

what is sequence conservation?

Answer 7

DNA sequence that is vital to the survival of an organism does not normally show much evidence of variation. Resistant to change
Most variants in these regions will be selected against as they are likely to have a strong deleterious effect

Question 8

Which sequences of DNA are most highly conserved?

Answer 8

Enzyme active sites
Structural regions of proteins
coding regions

Question 9

what affects frequency of genetic variation?

Answer 9

Selection
Mutation
Migration
Genetic Drift

Question 10

what is the main source of heritable changes in a species

Answer 10

genetic variation

Question 11

What is migration?

Answer 11

movement of species from a different population to an existing population - new variants enter the existing pool of variants = admixture. Population frequency of specific variants can change purely due to admixture and not be disease related

Question 12

what is genetic drift

Answer 12

how the frequency of variants changes in a population due to chance in recombination. Not all organisms will pass on their genetic variants to the next gen

Question 13

Which DNA sequences are moderately conserved?

Answer 13

Signal regions in 5’ and 3’UTRs

Promoters

Question 14

Which sequences are weakly conserved?

Answer 14

Enhancers (in introns and intergenic DNA)

3rd base of codons

Question 15

what can sequence conservation be used for?

Answer 15

Cross species comparison can be used to generate an evolutionary profile for a gene or gene family
Cross species conservation allows us to identify the important regions of a gene (and its protein)
This allows us to concentrate on areas that appear to be important in novel genes

Question 16

what do phylogenetic trees show?

Answer 16

Phylogenetic trees illustrate relatedness of different species/ strains/ sequences
The distance between two entities on a tree is related to how similar they are
closer = more similar
Distance is related to evolutionary pressures and to time

Question 17

use of phylogenetics in infectious disease

Answer 17

HIV may have been introduced via contaminated polio vaccine containing SIV. Using a phylogenetic tree, can determine which strain of SIV is most closely related to HIV to identify the source

Question 18

what is gene duplication

Answer 18

duplication of a DNA sequence containing a gene
Typical mechanism is unequal crossing over during meiosis
After duplication = 2 copies of the same gene on one chromosome. One copy can continue original function, while other copy can evolve new functions through changes in the coding sequence and/ or control sequences

Question 19

what is unequal crossing over

Answer 19

Recombination between sequences that are not the correct sequence but are very similar
Often low copy number repeat sequences

Question 20

what are the globin genes?

Answer 20

two clusters -
Alpha like are on chromosome 16
has 3 genes and 3 pseudogenes

Beta like are on chromosome 11
has 5 genes and 1 pseudogene

Question 21

What are the adult Hb compositions ?

Answer 21

alpha-2-beta-2

alpha-2-delta-2

Question 22

What changes occur to gamma gene from HbF to HbA?

Answer 22

the γ gene control sequences have evolved
so that γ-genes are expressed during foetal life

while the β-gene is expressed during postnatal life

Question 23

fetal hb is..?

Answer 23

alpha and gamma

Question 24

postnatal hb is..?

Answer 24

alpha delta and alpha beta

Question 25

what happens to the total % of Hb throughout development

Answer 25

alpha and beta conc is high at postnatal after birth, gamma reduces