Question

40 the diagram shows a pair of chromosomes from the same cell.

a gene is found at the point labelled p.
what will be found at the equivalent position labelled q in a heterozygous individual?
a a different allele of a different gene
b a different allele of the same gene
c a different gene of the same allele
d the same gene of the same allele

Explanation:

Identify homologous chromosomes

The diagram shows a pair of chromosomes from the same cell. Because they have the same size, shape, and structure, they represent a pair of homologous chromosomes. Homologous chromosomes carry genes controlling the same inherited characteristics at corresponding positions (loci).

Analyze the locus of the gene

The point labeled P represents a specific locus (position) of a gene on one chromosome. The point labeled Q is at the equivalent position (the same locus) on the homologous partner chromosome. Therefore, the locus Q must contain the same gene that is found at locus P.

Apply the definition of heterozygous

A heterozygous individual has two different alleles (variants) for a particular gene at a given locus. Since the individual is heterozygous for this gene, the allele at locus Q must be different from the allele at locus P.

Determine the correct option

Combining these facts, at the equivalent position Q in a heterozygous individual, we will find a different allele of the same gene. This matches option B.

Answer:

• A a different allele of a different gene
• B a different allele of the same gene (Correct answer)
• C a different gene of the same allele
• D the same gene of the same allele