Populations

Question 1

What is a population

Answer 1

A group of organisms of the same species occupying a particular place at the same time that can potentially interbreed

Question 2

What is a gene pool

Answer 2

The gene pool is the complete range of alleles present in a population

Question 3

What is a species

Answer 3

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

Species can exist as one or more populations

Question 4

What is allele frequency

Answer 4

How often an allele occurs in a population

Usually given as a percentage of the total population (e.g. 35%) or a number (0.35)

Question 5

What is the Hardy-Weinburg Principle

Answer 5

A mathematical model which predicts that the frequencies of alleles will not change from one generation to the next

This principle is only true under certain conditions; it has to be a large population, there must be no immigration, emigration, mutations or natural selection

Random mating must also occur with all possible genotypes being able to breed with others

The frequency of alleles, genotypes and phenotypes in a population can be calculated using the Hardy-Weinberg equation

The Hardy-Weinburg principle can predict the percentage of a population that has a certain genotype and show if external factors are affecting allele frequency

Question 6

How to use the Hardy-Weinburg Principle

Answer 6

Frequency of the dominant allele is noted p while that of the recessive allele is noted q

Both must account for the whole population (1.0), therefore: p + q = 1

p^2 + 2pq + q^2 = 1

p^2 = frequency of homozygous dominant genotype

2pq = frequency of heterozygous genotype

q^2 = frequency of homozygous recessive genotype

i.e. total frequency of all possible genotypes for a characteristic in a certain population is 1; frequencies of individual phenotypes add up to 1