Population Genetics Of Adaptation II

Question 1

What does population genetics let us understand?

Answer 1

Selection on standing variation

Question 2

Example of adaptive evolution

Answer 2

• the medium ground finches G. Fortis and G. Magnirostris occupy similar niches, eating large seeds
• in 2003, severe drought resulted in strong competition
• from 2004-2005 there was rapid evolution of small beaks in G. Fortis
• plotting g. Fortis beak size against year shows this

Question 3

What is the central dogma of modern genetics

Answer 3

DNA -> RNA -> Protein -> Phenotype

Question 4

If you plot mutation rate (per nucleotide per replication) against genome size what relationship do you see?

Answer 4

As genome size increases from
10^2 to 10^10, mutation rate decreases from 10^-2 to 10^-11 - strong negative linear correlation

Question 5

How does mutation affect selection

Answer 5

• mutation introduces new deleterious variation
• selection reduces frequency of the low fitness alleles

Question 6

Why do populations contain rare deleterious alleles?

Answer 6

• selective coefficients change as alleles become rare
• rare deleterious allele are ‘hidden’ from selection by heterozygosity
• spontaneous mutation continually recreates low fitness alleles

Question 7

Why do we need rapidly evoking systems?

Answer 7

Beneficial mutations are rare

Question 8

Give an example of a rapidly evolving system

Answer 8

Influenza

Question 9

Describe the rapid evolution of influenza

Answer 9

• HA gene undergoes rapid positive selection
• new amino acid fixations allow host antibody escape

Question 10

HA

Answer 10

haemagglutin

Question 11

Why are microbes good for studying by evolution

Answer 11

• small
• short génération time (can see phylogeny evolve in real time)
• small genomes
• cryogenic freezing
• measure fitness

Question 12

What is the generation time of a microbe?

Answer 12

20-30mins

Question 13

How much does it cost to sequence a microbial genome?

Answer 13

50 squids

Question 14

How do we measure fitness in bacteria?

Answer 14

• genetic tagging with floruedfent protein
• allows comparison between ancestral and evolved bacteria through competition by measuring density

Question 15

How do we conduct long term experimental evolution studies?

Answer 15

• grow a culture in tube for 24h
• growing in new tube each 24h cycle
• repeat
• keep one sample back in fridge: the frozen fossil record

Question 16

Transitions to asexuality are

Answer 16

An evolutionary dead-end

Question 17

Give examples of asexual organisms

Answer 17

• Bdelloid rotifer
• Cnemicdophorus uniparens

Question 18

Describe the lifespan of asexual species

Answer 18

Usually short

Question 19

Does recombination accelerate adaption?

Answer 19

• without recombination, beneficial mutations compete with each other
• recombination can accelerate evolution by bringing together beneficial mutations

Question 20

Why does the flu return every year?

Answer 20

directional sweeps

Question 21

Asexuals exist at the

Answer 21

Tips of phylogeny