Question

Which protein is called “guardian of the genome ”?
A. P53
B. Cyclin D
C. CDK 4
D. Rb

Answer 1

Hint: Genome is the genetic material of an organism. It consists of DNA (or RNA in RNA viruses). The study of genomes is called genomics.

Complete Answer:
Let us analyse each given option to find out the correct answer.
Option A: P53 has been called the “guardian of the genome" because of its role in conserving stability by preventing genome mutation. The name is due to its molecular mass, i.e., it is in the 53 kilodalton fraction of cell proteins. It stops the cells that are mutated or damaged DNA from dividing. p53 helps in preventing the development of tumors. This protein is found inside the nucleus of cells. It is also essential for regulating DNA repair and cell division.

Option B: Cyclin D is a member of the cyclin protein family. It is involved in regulating cell cycle progression. The synthesis of cyclin D is initiated during G1 and drives the G1/S phase transition.

Option C: Cyclin-dependent kinase 4 is also known as cell division protein kinase 4. It is an enzyme that in humans is encoded by the CDK4 gene. CDK4 is a member of the cyclin-dependent kinase family.

Option D: The Rb protein is a tumor suppressor. It plays a pivotal role in the negative control of the cell cycle and in tumor progression. It is also responsible for major G1 checkpoints, blocking S-phase entry, and cell growth.

Thus, the correct option is A, P53.

Note: It is to be noted that the human p53 gene is located on the seventeenth chromosome. It is a phosphoprotein made of 393 amino acids. Mutations in p53 cause change in single amino acids, which leads to the production of an altered version of the protein that cannot control cell proliferation and is unable to trigger apoptosis in cells with mutated or damaged DNA.