Molecular Basis of Inheritance
Nucleic acids are long polymers of nucleotides. While DNA stores genetic information, RNA mostly helps in transfer and expression of information. DNA, being chemically and structurally more stable, is a better genetic material. However, RNA is thought to have evolved first. DNA replicates semiconservatively. During transcription, one strand of DNA acts as template to direct the synthesis of complementary RNA. The genetic code is read again on the principle of complementarity by tRNA, which acts as an adapter molecule. Protein synthesis is done by ribosomes. Both transcription and translation are energetically very expensive processes. Regulation of gene expression refers to a very broad term that may occur at various levels. The genes in a cell are expressed to perform a particular function or a set of functions. Human Genome Project was a mega project that aimed to sequence every base in human genome. Many new areas and avenues have opened up as a consequence of the project.
z gene codes for............... in lac operon.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Beta-galactosidase
The lac operon of E. coli has one regulatory gene, i, and three structural genes, z, y and a. All three structural genes are needed to use lactose.
(1) Permease — Incorrect. It is coded by the y gene. It lets lactose enter the cell.
(2) Transacetylase — Incorrect. It is coded by the a gene.
(3) RNA polymerase — Incorrect. It is not coded by a gene of the lac operon. It is the enzyme that transcribes the operon.
(4) Beta-galactosidase — Correct. The z gene codes for it. It breaks down the disaccharide lactose into galactose and glucose.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
The Lac Operon – …
