Microevolution - Lecture 8

Question 1

What is microevolution?

Answer 1

Changes in the gene pool of a population of organisms over time

Question 2

What is the gene pool?

Answer 2

○ All alleles of all individuals in a population
○ Represents all of the genetic variation in a population

Question 3

How is microevolution different to macroevolution?

Answer 3

Macroevolution:
○ Major evolutionary events above the level of the species e.g. the evolution of major animal groups
○ Speciation
Microevolution:
○ Evolutionary events within a species or population
○ Microevolution plus chance events gives rise to macroevolution

Question 4

What does evolution by natural selection require?

Answer 4

○ Differential reproductive success
○ Genetic variation

Question 5

What is the study of microevolution called?

Answer 5

○ Population genetics
○ A synthesis of Darwin’s theory of evolution by natural selection with Mendel’s theory of inheritance

Question 6

What can population genetics tell us about evolving humans pathogens?

Answer 6

○ Bacteria: antibiotic resistance
○ Viruses: resistance to antiviral drugs
○ Emerging new pathogens

Question 7

What was significant about the Spanish flu?

Answer 7

○ Had a high case fatality rate (CFR)
○ CFR = The proportion of people infected that died

Question 8

When did SARS-CoV-2 first infect humans?

Answer 8

○ Time to most recent common ancestor: 24 November 2019

Question 9

Where did SARS-CoV-2 come from?

Answer 9

○ Diverged from a similar bat virus 40-70 years ago
○ Most similar CoV to SARS-CoV-2 is from horseshoe bat (96%)

Question 10

What can population genetics tell us about human evolution in response to pathogens?

Answer 10

Heterozygous form of both thalassemias (alpha and beta) give resistance to the malaria parasite

Question 11

What can population genetics tell us about the genetic structure of wild populations

Answer 11

○ How much genetic diversity is present in a population
○ How it is distributed
○ The response of a population to change

Question 12

How is the gene pool studied?

Answer 12

○ Look at one gene at a time
○ Use a single gene locus model
○ Measure allele frequency and genotype frequency

Question 13

How to measure allele frequency?

Answer 13

Number of allele of one type/Total number of alleles

Question 14

How to measure genotype frequency?

Answer 14

Number of individuals of one genotype/Total number of individuals

Question 15

What is the Hardy-Weinberg equilibrium?

Answer 15

○ p^2+2pq+q^2 = 1
○ p = dominant homozygous frequency (AA)
○ 2pq = heterozygous frequency (Aa)
○ q = recessive homozygous frequency (aa)

Question 16

What are the requirements for Hardy-Weinberg equilibrium?

Answer 16

○ Population size is large
○ Mating is random
○ No migration from other populations
○ No selection
○ No mutation (ignore if measured over a short period of time)

Question 17

What factors can lead to changes in allele and genotype frequencies?

Answer 17

○ Genetic drift (low population size)
○ Non-random mating
○ Migration/gene flow
○ Selection

Question 18

How is genetic variation preserved?

Answer 18

Natural selection:
○ Balancing selection
- Heterozygote advantage
- Frequency dependent selection
○ Different selective pressures across the geographic range of the population
○ Neutral theory (Motoo Kimura)