G&E: Hardy-Weinberg Principle

Question 1

Species

Answer 1

A group of similar organisms that can reproduce to give fertile offspring.

Question 2

Population

Answer 2

Group of organisms of the same species living in a particular area at a particular time - have the potential to interbreed.

Question 3

Allele frequency

Answer 3

How often an allele occurs in a population.

Usually given as a percentage of the total population.

Question 4

Gene pool

Answer 4

Complete range of alleles present in a population.

Question 5

What are the certain conditions needed for the Hardy - Weinberg Principle to be true?

Answer 5

• Large population.
• No immigration, emigration, mutation or natural selection.
• Needs to be random mating - all possible genotypes can breed with all others.

Question 6

Hardy - Weinberg principle

Answer 6

A mathematical model that predicts that the frequencies of alleles in a population won’t change from one generation to the next.

Question 7

What can the Hardy - Weinberg equations be used for?

Answer 7

To calculate the frequency of particular alleles, genotypes and phenotypes within populations.

Also to test HW principle applies to particular alleles in particular populations - eg. to test whether selection or any other factors are influencing allele frequency.

Question 8

When can you use the HW equations?

Answer 8

When a gene has two alleles, you can figure out the frequency of one of the alleles of the gene if you know the frequency of the other allele.

Question 9

In the HW equation, what is p?

Answer 9

The frequency of one allele, usually the dominant one.

Question 10

In the HW equation, what is q?

Answer 10

The frequency of the other allele, usually the recessive one.

Question 11

What is the total frequency of all possible alleles for a characteristic in a certain population?

What does this mean?

Answer 11

1. 0
   * So, the frequencies of the individual alleles must add up to 1.0.*

Question 12

What is the HW equation used to predict allele frequency?

Answer 12

p + q = 1

Question 13

What is the HW equation you would use to figure out the frequency of one genotype?

Answer 13

p² + 2pq + q² = 1

Question 14

In the HW equation what is p²?

Answer 14

The frequency of the homzygous dominant genotype.

Question 15

In the HW equation what is 2pq?

Answer 15

The frequency of the heterozygous genotype.

Question 16

In the HW equation, what is q²?

Answer 16

The frequency of the homozygous recessive genotype.

Question 17

p² is the homozygous dominant genotype frequency if what?

Answer 17

p is the dominant allele.

Question 18

How can phenotype frequencies be calculated?

Answer 18

Using genotype frequencies.

Question 19

The frequency of cystic fibrosis (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 (Ff):

Answer 19

Calculate q:

• ff frequency is 1 in 2500
• so, ff = q² = 1 / 2500 = 0.0004
• so, q = 0.02

Calculate p:

• p+q = 1
• p= 1 - q
• p = 1 - 0.02 = 0.98

Calculate 2pq:

• 2pq = 2 x 0.98 x 0.02 = 0.039

So percentage of UK population that are carriers is 3.9%