AIIMS 2019 Biology Gene Library MCQ Question

A DNA library specifically refers to a collection of cloned DNA fragments that represent the entire genome of an organism, which can include both genomic DNA and complementary DNA (cDNA) derived from mRNA. Option C is correct because a cDNA library is a specific type of DNA library that contains only cDNA, synthesized from mRNA, thus representing expressed genes in a cell at a given time.

Option A is incorrect as a gene library focuses on DNA, not RNA, while option B is misleading because a gene library encompasses multiple genes, not just one. Option D is also incorrect since a gene library typically represents the genes of a single organism or a specific set of organisms, rather than all possible genes of all organisms.