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Question 19 of 38

Q.In S phase of the Cell Cycle:

(a) Chromosome number is increased
(b) Amount of DNA is reduced to half in each cell
(c) Amount of DNA doubles in each cell
(d) Amount of DNA remains same in each cell
Tamil Nadu DgeTamil Nadu HSC First Year (DGE) Board 2019MCQ· 1mImportance★★★★★
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During S phase, DNA replication doubles the amount of DNA in the cell, though the chromosome number does not change until cell division actually separates the chromatids.

The cell cycle is divided into Interphase (G1, S, G2) and M phase (mitosis/cytokinesis):

  • G1 phase — cell grows, synthesises RNA and proteins, prepares for DNA replication; DNA content is the normal diploid (2C) amount.
  • S phase — DNA replication (synthesis) takes place; every chromosome is duplicated, so the DNA content doubles from 2C to 4C. Importantly, the CHROMOSOME NUMBER does not increase in S phase — each chromosome simply now consists of two identical sister chromatids joined at the centromere, so the count of chromosomes is unchanged even though DNA content has doubled. …

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