# Topic 8.2 - Populations Flashcards

1
Q

Define allele frequency

A

How frequently a particular allele appears in a population

2
Q

Define gene pool

A

All the alleles of all the genes of all the individuals in a population at any one time

3
Q

Define genetic bottlenecks

A

Event that causes big reduction in population

4
Q

Describe how genetic bottlenecks reduce genetic diversity

A
• Reduces number of different alleles in gene pool = reduces genetic diversity
• Survivors reproduce and larger population is created from few individuals
5
Q

Describe how selective breeding reduces genetic diversity

A
• Individuals with desired characteristics are breed together to pass on the desired alleles
• So alleles (for less desirable characteristics are removed)
• Variety of alleles within population is deliberately restricted to small no. of desired alleles
• Leads to population that possess only desired alleles
6
Q

What does the Hardy-Weinberg principle predict?

A

Predicts the frequencies of alleles in a population won’t change from one generation to the next

7
Q

Name 4 assumptions that the Hardy-Weinberg principle makes

A
• Population is very large
• Mating is random within population
• There is no selective advantage for any genotype
• There is no mutation
8
Q

Name the 2 uses of the Hardy-Weinberg equations

A
1. Used to calculate frequency of particular alleles, genotypes and phenotypes within populations
2. Used to test whether or not Hardy-Weinberg principle applies to particular alleles in particular population
• If frequencies do change between generations in a large population = influence of some kind
9
Q

State the Hardy-Weinberg equation for predicting allele frequency

A

p + q = 1

10
Q

State the Hardy-Weinberg equation for predicting genotype and phenotype frequency

A

p squared+ 2pq + q squared = 1

11
Q

State what p & q represent in this equation:

p + q = 1

A
• p = frequency of dominant allele A
• q = frequency of recessive allele a
12
Q

State what p squared, q squared & 2pq represent in this equation:

p squared + 2pq + q squared = 1

A
• p squared = frequency of homozygous dominant AA
• q squared = frequency of homozygous recessive aa
• 2pq = frequency of heterozygous Aa/aA
13
Q

The frequency of cystic fibrosis (genotype ff) in the UK is currently approximately 1 birth in every 2500. Estimate the percentage of people in the UK that are cystic fibrosis carriers.

A
14
Q

If the frequency of cystic fibrosis is measured 50 years later it might be found to be 1 birth in 3500. Estimate the frequency of the recessive allele (f) in the population.

A
15
Q

An allele W, for white wool, is dominant over allele w, for black wool. In a sample of 900 sheep, 891 are white and 9 are black. Calculate the allelic frequencies within this population, assuming that the population is in H-W equilibrium.

A

q squared = 0.01

q = 0.1

p + 0.1 = 1

p = 0.9

16
Q

What is the evidence from the table that non-agouti and blotched are alleles of different genes? (1)

A

In Paris / London frequencies (of these alleles) add up to more than 1

e.g. 0.71 + 0.78 = 1.49