Question

A population is said to be polymorphic for a locus if it has at least

• A. Three genotypes for that locus.
  
• B. Two genotypes for that locus.
• C. Two genotypes for that locus, the rarest of which is more common than expected by mutation alone.
• D. None of the above

Answer 1

Answer: (B)

Two genotypes for that locus.

Polymorphic locus is the location within a gene that has a large number of possible sequences. An example of a ploymorphic locus would be 'Human Leukocyte Antigen genes', which have many possibilities for a genotype. So, a population is said to be polymorphic for a locus if it has at least two genotypes for that locus.
Polymorphic locus does not means two different alleles at that locus, three genotypes for that locus and two genotypes for that locus.

Thus, the correct answer is option B.