populations

Question 1

What is a population?

Answer 1

A group of organisms of the same species in one area at one time that can interbreed

Question 2

What is a gene pool

Answer 2

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

Question 3

What is allele frequency

Answer 3

Proportion of an allele of a gene in a gene pool (decimal or percentage)

Question 4

What does the Hardy-Weinberg principle state and what are the conditions
under which the principle applies?

Answer 4

● Allele frequencies will not change from generation to generation, given:
○ Population is large
○ No immigration / emigration (to introduce / remove alleles)
○ No mutations (to create new alleles)
○ No selection for / against particular alleles
○ Mating is random

provides a mathematical model

Question 5

What is the Hardy-Weinberg equation?

Answer 5

p^2 + 2pq + q^2 = 1
This can be used
simultaneously with:
p + q = 1

● p = frequency of one (usually dominant) allele of the gene
● q = frequency of the other (usually recessive) allele of the gene
● p^2 = frequency of homozygous (usually dominant) genotype
● 2pq = frequency of heterozygous genotype
● q^2 = frequency of homozygous (usually recessive) genotype

Question 6

The gene for the Rhesus blood group has two alleles. The allele
for Rhesus positive, R, is dominant to that for Rhesus negative, r.
16% of the population of Europe is Rhesus negative. Use the
Hardy-Weinberg equation to calculate the percentage of this
population that you would expect to be heterozygous for the
Rhesus gene

Answer 6

Find q^2
q^2 = 16% = 0.16
Find q
q = √0.16 = 0.4
Find p
p = 1 - 0.4 = 0.6
Find 2pq
2 x 0.4 x 0.6 = 0.48
Convert 48%

Question 7

In one species of flowering plant, two alleles C^R (red)
and C^W (white) code for flower colour. When both arepresent, flowers are pink.
A population contained 9% red-flowered plants. Use the
Hardy-Weinberg equation to calculate the percentage
of pink-flowered plants in this population

Answer 7

Find q^2
q^2 = 9% = 0.09
Find q
q = √0.09 = 0.3
Find p
p = 1 - 0.3 = 0.7
Find 2pq
2 x 0.3 x 0.7 = 0.42
Convert
42%

Question 8

In fruit flies, a gene for body colour has a
dominant allele G (grey) for and a recessive
allele g (black).
A population contained 64% grey-bodied flies.
Use the Hardy–Weinberg equation to calculate
the percentage of flies heterozygous for this
gene.

Answer 8

Find q^2
p^2 + 2pq = 64% = 0.64
so q^2 = 1 - 0.64 = 0.36
Find q
q = √0.36 = 0.6
Find p
p = 1 - 0.6 = 0.4
Find 2pq 2 x 0.6 x 0.4 = 0.48
Convert
48%