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Question

Biology Question on cell cycle and cell division

Duplication of DNA occurs during which stage of the cell cycle?

A

Interphase

B

Early prophase

C

Late prophase

D

Late telophase

Answer

Interphase

Explanation

Solution

Interphase is the stage between two successive cell divisions. During interphase, chromosomes are decondensed and are distributed throughout the nucleus. It is the largest period in the cell cycle and is divided into three phases - G1,SG_1 , S and G2G_ 2 . During G1G_1 -phase (or post -mitotic phase) the cell grows and synthesis of tRNA, m RNA, ribosomes, enzymes and proteins necessary for DNA synthesis occurs. During S-phase or synthetic phase the replication of DNA takes place. For replication of DNA histone proteins are required so they are also synthesized during this phase. It takes about 30%-50% of the total cell cycle. The nucleotides get assembled and DNA molecules are synthesised. During G2G_2 -phase (or pre-mitotic phase) organelles like centrioles are doubled and mitochondria, chloroplasts etc. divide.