Question

A genomic library _____.

a) contains only protein-coding DNA sequences
b) is built from mRNA by reverse transcription
c) is a storehouse of protein structures for a specific organism
d) contains all of an organism's DNA
e) is best constructed from very short DNA fragments

Answer 1

A genomic library is a storehouse of an organism's entire DNA, constructed by cloning genomic fragments. To focus on expressed genes, researchers create libraries using mRNA instead of genomic DNA. cDNA libraries contain DNA from only expressed genes, excluding introns and control sequences.

Step-by-step explanation:

A genomic library is a storehouse of an organism's entire DNA. It is constructed by cloning genomic fragments into plasmid vectors or bacteriophage. Different tissues express different genes, so to focus on the expressed genes in an organism, researchers construct libraries using the organism's messenger RNA (mRNA) instead of genomic DNA.

This mRNA is reverse transcribed into complementary DNA (cDNA), which is then used to make double-stranded DNA copies. The benefit of a cDNA library is that it contains DNA from only the expressed genes, excluding introns and control sequences.