Hardy Weinberg

• Biologie
• Middelbare school
• vwo
• Leerjaar 4

Evolution

 

Hardy-Weinberg equilibrium

Remember the five fingers of evolution: What are the five processes that lead to evolution?

Five processes that lead to evolution

1. Small population/genetic drift: chance will start to play a role
2. Non-random mating/sexual selection
3. Mutation
4. Gene flow: immigration and emigration 
5. Natural selection 

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Question

A short-haired heterozygous cat mates with another short-haired heterozygous cat. The gene for short-haired is dominant. What are the chances on a heterozygote? What are the chances on a short-haired cat? 

What is the total chance on a short-haired or long-haired cat?

What is a population?

What is a gene pool?

Hardy-Weinberg: waar komt het vandaan?

Look at the following formula:

this calculates?

p​2​​+2pq+q​2​​=1

Question

In sheep, a white coat is produced under the influence of the dominant allele H and a black coat due to the recessive allele h. In a flock of sheep, 891 have white and 9 have black fur.

The Hardy-Weinberg rule applies to this population.

Calculate the frequency of the allele H.

Total number of sheep: 891 + 9 = 900

Frequency animals with black fur: 9/900=0.01 = q2

-> q = 0.1

-> p = 0.9 (frequency of allele H)

Question

In a population of 100 birds, the allele frequency for the recessive white-wing allele is 0.4.

How many birds in that population have white wings?

q = 0.4

-> q2 = 0.16

-> number of birds with white wings: 0.16 x 100 = 16

Did you achieve these learning objectives?

- You can explain what the Hardy Weinberg principle is used for in evolution.

- You can explain what the five conditions are for the Hardy Weinberg equilibrium to remain constant.

- You can use the Hardy-Weinberg equation to calculate genotype and allele frequencies from observed phenotype frequencies.

Work to be done

Biozones 209 - 212

2 fill-in worksheets to help you to make a summary of 15.3 

Albinism occurs with a frequency of 1/20,000 people. How many people are carriers?

Albinism in 1 on 20.000 people

According to Hardy Weinberg's equilibrium:

p2 + 2pq + q2 = 1 and p + q = 1

Albinism is the phenotype of aa -> frequency q2

-> q2 = 1/20,000 = 0.00005

-> q = 0.007 (p+q=1) p = 1 - 0.007 = 0.993

-> frequency carriers: 2pq = 2 x 0.007 x 0.993 = 0.00139

-> in a population of 20,000 people: 0.00139 x 20,000 = 278 carriers