Question

During in class we did a simulation of the effect of natural selection in a population. After eliminating the individuals that died of, because of predation or disease, we calculated the frequencies of p and q. Then the number of individuals was restored to the initial population number of 50. Why was this crucial in our simulation?

Answer 1

• Hardy-Weinberg equation describes: The most possible distribution of the population genotype of the population, if the frequencies of the alleles are known.
• If allele frequencies are p and q, then the genotype frequencies are p2, q2, 2pq.
• A population is considered to be in Hardy-Weinberg equilibrium when: In a randomly mating population, allele frequency and genotype frequency remain constant.
• Thus, under Hardy-Weinberg equilibrium:

p+ q=1 and

p2+2pq + q2 = 1.

• In a population, there may be selection of few alleles that results in survival of few individual in a population, while some alleles may be entirely eliminated or lost or some deleterious alleles may be incorporated.
• Allele frequency changes, from the initial frequency.
• This leads to random selection of an allele through natural selection, which is established in the population and increases its frequency, until the normal numbers are regained.

Since, allele frequency changes, due to forces of evolution like natural selection, the Hardy-Weinberg equilibrium alters in the population.

Thus, the value of p and q (allele frequencies) to match the predicted values as per Hardy-Weinberg equilibrium, the initial population number should be regained.

Thus, for allele frequencies under Hardy-Weinberg equilibrium, certain evolutionary forces are considered to be constant.

Assumptions:

• Population is randomly mating.
• Population size is infinitely large.
• No natural selection.
• No mutation to create new allele.
• No migration (closed population- no immigration or emigration).
• No genetic drift.
• No genetic shift.
• No gene flow.