Population Genetics

Question 1

use the Hardy-Weinberg Principle (HWP) to calculate:
Gene and genotype frequencies
To know the assumptions of the Hardy-Weinberg Principle
To understand how rare recessive alleles are maintained in populations
To become familiar with examples of when the HWP can be applied

Question 2

understand the basic principles underlying the transmission of genes from generation to generation in populations

Answer 2

• gene frequency and population size will affect the fitness of individuals carrying particular genes

Question 3

What is the definition of population?

Answer 3

“group of sexually interbreeding individuals”

Question 4

What causes genetic variation?

Answer 4

• Mutation/substitution (change in DNA sequence) cause genetic variation
• Recombination

Question 5

WHAT INFLUENCES THE FREQUENCY
OF THAT VARIATION?

Answer 5

• Natural selection
• Migration (animals entering or leaving populations)
• Genetic drift (random changes in small population)

Question 6

What is the HARDY-WEINBERG PRINCILE?

Answer 6

allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary factors

It Explains why recessive genes do not disappear over time explains how genes are maintained in populations

HWP assumptions:
- Random mating
- Large population
- No natural selection
- No mutation
- No migration

p+q have to add up to 1
(p + q)2 = p2 + 2pq + q2 = 1 (see slide 10)
q = recessive homozygous phenotype (e.g. tt)
p = Dominant homozygous phenotype (e.g TT)

Allele frequencies are calculated using the formula:
Allele frequency = frequency (homozygotes) + ½ frequency (heterozygotes) (slide 13)

Slide 20 explanation: q2 = 1/20000 (0.00005) q = the square root of 1/200000. The dominant gene frequency must then add up to 1, so 1-q is done to find the dominant gene frequency. The next part is plugging the numbers into the HBP equation ( (p + q)2 = p2 + 2pq + q2)

When there are multiple alleles use:
p2(A1A1) + 2pq(A1A2) + 2pr(A1A3) + q2(A2A2) + 2qr (A2A3) + r2(A3A3) = 1

PRACTICE QUESTIONS on powerpoint 2, there is also an answer powerpoint and recording that explains how the answers were achieved.