Question

Which of the following event occurs during $G_1$ -phase?

• A. DNA replication
• B. Growth and normal function of cell
• C. Mutation
• D. Fertilization

Answer 1

Answer: (B)

$G_1$ -phase is called as pre-synthetic phase or post-mitotic phase. It is the longest phase of cell cycle. In $G_1$ -phase a cell has two options
[a] Continues cycle and enters S-phase.
[b] Stops cell cycle and enters $G_0$ -phase for undergoing differentiation. DNA replication is the formation of exact replica or carbon copy of DNA to make DNA copies. It is an autocatalytic function of DNA. Mutation is the alteration in chromosom structure or number and also an alteration in genes due to change in DNA composition. It provides new alleles and, therefore, underlies all other mechanisms that produce variations, the raw material for evolution. Fertilization is the process of fusion of male and female gametes, ie, sperm and ovum forming a zygote. It can be external (outside the body of female) or internal (inside the body of female).