Lecture 10

Question 1

polygenic trait

Answer 1

Influenced by many genetic loci
1. Interaction between alleles (epistasis)
2. Interaction with environment (phenotypic plasticity)

Question 2

Quantitative genetics

Answer 2

study of the genetics and genomics of continuous phenotypic traits

Question 3

Definition of a Population (Krebs, 2001)

Answer 3

A group of organisms of the same species occupying a particular space at a particular time.

Question 4

How can populations be differentiated genetically?

Answer 4

Populations can be distinguished by allele frequencies at DNA markers, which differ from nearby conspecific groups (e.g., Fst > 0.05 in marine species, Fst > 0.2 in freshwater fishes).

Question 5

What is Fst, and why is it important in defining populations?

Answer 5

Fst (Fixation Index) measures genetic differentiation between populations. A higher Fst indicates greater genetic separation.

Question 6

trait

Answer 6

a character of a species
- eye colour, height, weight

Question 7

phenotype

Answer 7

measurable traits of an organism, resulting from an interaction between its genotype and its environment
(what selection acts on)

Question 8

phenotypic plasticity

Answer 8

variation in the phenotype due to environmental factors
- same genotype has different phenotypes

Question 9

selection

Answer 9

differential survival/fecundity of some phenotypes

Question 10

migration

Answer 10

movement of individuals and genes from one local population to another

Question 11

equation for selection differential

Answer 11

S = xB - xP
xB = trait mean in the population before selection
xP = trait mean in the population after selection

Question 12

why does the sign of selection differential (S) matter

Answer 12

• because it indicates the direction of selection on a trait
  (+S) - trait is under positive selection - individuals with higher trait values will have higher fitness
  ex: if a larger beak leads to higher survival, beak size will increase
  (-S) - trait is under negative selection - individuals with lower trait values have nigher fitness
  ex: if smaller body size reduces energy needs and increases survival, average body size may decrease

Question 13

genetic drift

Answer 13

is a random change in allele frequencies in a population over time. not because of natural selection
- stronger in smaller generations
- can lead to loss of genetic diversity
- due to random events
- can cause alleles to become fixed (100% frequency)