Question

Genetics: A Conceptual Approach Reacing Quiz MHE/Freeman Gth Edition Assume that a cell has 6 chromosomes while it is in the Gi stage of the cell cycle. How many chromosomes and how many DNA molecules will it have in the G2 stage? O O O O O 6 chromosomes and 12 DNA molecules 12 chromosomes and 12 DNA molecules 3 chromosomes and 6 DNA molecules 6 chromosomes and 6 DNA molecules 12 chromosomes and 24 DNA molecules

Answer 1

When cell cycle progresses to G₂ the number of chromosome remains same but the number of DNA molecules increases.

The number of DNA increases when DNA replicates and it decreases when a cell divides.

The number of chromosomes increases only when sister chromatids separate ( anaphase of mitosis and anaphase II of meiosis) and decreases when a cell divides.

Hence, the options (b), (c), (d) and (e) are incorrect answers.

Initial chromosome number is 6.

At G_2, there will be no change in the chromosome number.

The number of chromosomes will be 6 and the number of DNA molecules will be 12 (DNA replicates in S phase).

Note: Each chromosome has two chromatids or we can say that two DNA molecules are held at a common centromere.

Hence, the option ('a': 6 chromosomes and 12 DNA molecules) is the correct answer.