Question

Imagine that we are studying the colour coat of a population of chamoix in the Alps. There are two morphs, white and dark brown, which we know to be genetically determined.

(a) We observe that the frequency of brown decreased quite substantially between 2010 and 2011. Give 4 different potential explanations for this decrease

(b) Imagine that we observe that the frequency of brown varies erratically over the next 4 years. Give two potential explanations for the changes in the frequency of brown

Answer 1

a) 4 potential explanationa are for decrease of brown coat colour may be-

1. Genetic variation- this is is caused by:

• mutation
• random mating between the chamoix
• random fertilization
• crossing over (or recombination) between chromatids of homologous chromosomes during meiosis

2. Genetic drift- this is the change in allele frequencies of a population due to random chance events, such as natural disasters, calamity etc.

3. Geographical barrier- populations are geographically separated by environmental barriers or when they are under selection pressures from a different environment.

4. Environmental change- Phenotypes are also influenced by other factors, such as the environment, like increase or decrease in pollution, temperature dependant sex determination etc.

b) Two potential explanations for the changes in the frequency of brown, may be 2 different theories of genetic drift as follows-

• The bottleneck effect occurs when a natural disaster or similar event randomly kills a large portion (i.e. random sample) of the population, leaving survivors that have allele frequencies that were very different from the previous population.
• The founder effect occurs when the (i.e. “founders”) separates from the old population to start a new population with different allele frequencies.