In a long term experiment on a population of Drosophila melanogaster, the frequency of two alleles '

Question

In a long term experiment on a population of Drosophila melanogaster, the frequency of two alleles ' $a$ ' and ' $b$ ' on a multi-allelic locus $X$ over time has been shown in the following graph.\ 6 students were asked to evaluate the observed pattern and their inferences are given below.\ Student 1 : Environment is not uniformly selective.\ Student 2 : Population may be under artificial selection.\ Student 3 : Genetic variability is progressively reduced.\ Student 4 : Genetic variability is progressively increased.\ Student 5 : Mechanism such as genetic drift is operating from time to time.\ Student 6 : Selection is favouring a particular genotype through directional selection.\ The appropriate conclusions were drawn by\

Professor PC Thomas Classes · Answer

(c) : According to the given graph, the environment must be uniformly selective since it is leading to increase and decrease in frequency of alleles ' $a$ ' and ' $b$ ' respectively. Therefore, genetic variability is reducing at a very fast rate, it could be a result of artificial selection. Genetic drift does not seem to operating time to time because drift is caused by a chance event rather a directed selective process. Here, selection is favouring a particular genotype, since frequency of allele ' $a$ ' is increasing through the generations.