Question

The locus of mutation is

• A. Gene
• B. Chromosome
• C. Centromere
• D. Nucleus

Answer 1

Answer: (A)

Gene

Genes are the stretch of DNA that specify a particular protein and thereby control a specific trait in the organism; they are the unit of heredity. A mutation in the gene is manifested in its governed protein’s structure and function which in turn now express the mutant trait. Thus, genes are the loci of mutation; option A is the correct answer. Genes are arranged in a linear manner on chromosomes; the presence of specific genes imparts specific governing traits to chromosomes. For example, the presence of SRY gene on Y-chromosome make it sex determinant chromosome in human; thus chromosomal mutations are due to mutations in the genes present on them which makes option B incorrect answer. The centromere is the primary constriction of chromosomes that holds two chromatids together and is not the unit of heredity; option C is the incorrect answer. A nucleus is a double membrane bound eukaryotic organelle wherein the complete set of genes, composed of DNA is stored and replicated; option D is an incorrect answer. The correct answer is A.