L-21

Question 1

What is a population?

Answer 1

A localised group of individuals of the same species

Question 2

What is a gene pool?

Answer 2

The total aggregate of genes (and their alleles) in the population at one time

Question 3

Why do we need to estimate frequencies of genotypes in a population?

Answer 3

• to predict how many individuals will inherit a genetic disease
• to estimate the proportion of individuals who are “carriers” of genetic disease

Question 4

What is the Hardy-Weinberg equation?

Answer 4

P^2+ 2pq + q^2 = 1

Question 5

What is p in the Hardy Weinberg equation? What is q

Answer 5

• frequency of dominant allele

- frequency of recessive allele

Question 6

What can changes in allele frequency be caused by?

Answer 6

• non-random mating (assortative mating, inbreeding)
• random genetic drift
• bottleneck effect
• founders effect
• natural selection
• gene flow or migration
• mutation

Question 7

What is random genetic drift?

Answer 7

random change in allele frequencies due to sampling error over generationa

Question 8

What is the bottleneck effect?

Answer 8

A sharp reduction in the size of a population due to environmental events ( famines, earthquakes…) that can cause dramatic change of allele frequency or even loss of certain alleles

Question 9

What is the founder effect?

Answer 9

The loss of genetic variation that occurs when a new population is established by a very small number of individuals from an original larger population

Question 10

What is stabilising selection?

Answer 10

• selection where medium sized individuals are favoured by natural selection
• normal distribution peak gets higher and narrower
• mean remains unchanged

Question 11

What is directional selection?

Answer 11

• natural selection where larger or smaller individuals are favoured
• changes the mean value towards one extreme

Question 12

What is disruptive selection?

Answer 12

• natural selection where larger and smaller individuals are favoured
• two peaks form

Question 13

What is sexual selection?

Answer 13

• Individuals are favoured that have traits that are desirable to potential mates so have increased frequency in the next generation

Question 14

What is frequency dependent selection?

Answer 14

Natural selection where individuals with less common alleles are favoured so they become more common and less desirable in the net generation

Question 15

What is a Cline?

Answer 15

The gradual geographic change in genetic/ phenotypic composition

Question 16

What are the two ways that changes to population genetic variation occur?

Answer 16

• variation

- migration

Question 17

What are the 4 effects of migration?

Answer 17

• brings new alleles to a population
• changes proportions of existing alleles
• changes population size
• makes two populations more similar