Question

In a long term experiment on a population of Drosophila melanogaster, the frequency of two alleles ${}^{\prime }{a}^{\prime }$ and ${}^{\prime }{b}^{\prime }$ of 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

• A. Students $2,5$ and $6$
• B. Students $1,3$ and $5$
• C. Students $2,3$ and $6$
• D. Students $1,3$ and $6$

Answer 1

The correct option is C Students $2,3$ and $6$

According to the given graph, the environment must be uniformly selective since it is leading to increase and decrease in frequency of alleles ${}^{\prime }{a}^{\prime }$ and ${}^{\prime }{b}^{\prime }$ 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 ${}^{\prime }{a}^{\prime }$ is increasing through the generations.

So, the correct answer is 'Students $2,3$ and $6$'.