Respuesta :
Answer:
The correct answer is both.
Explanation:
- Each chromosome is made up of a pair of sister chromatids which remain attached to each other at the centromere.
- During DNA replication the DNA duplicates, which means that if initially in the parent cell 'n' chromosomes were present then, after duplication, the number of chromosomes in the cell will be '2n'.
- As mentioned above, each chromosome has a pair of sister chromatids, that is, two chromatids per chromosome. So, 'n' chromosomes will have '2n' chromatids. Hence, '2n' chromosomes will have '4n' chromatids.
- In a parent cell,
- Before duplication, number of chromosome = n, number of chromatid = 2n.
- After duplication, number of chromosome = 2n, number of chromatid = 4n.
- The cell cycle proceeds as, G0, G1, S, G2, M.
- G0 represents the interphase. It occurs before replication or duplication of the chromosomes, which occurs in the S phase.
- So, in G0 phase, the chromosome number is 'n' and chromatid number is '2n'.
- The number of chromatids changes after the cell duplicates its genetic material in interphase.
- Two chromatids each is expected to be in each human cell.
DNA REPLICATION:
- DNA replication is the process by which the DNA of a cell is doubled prior to cellular division.
- DNA replication occurs at the S-phase of the interphase stage of mitosis and meiosis. The DNA is doubled and represented by an increase in number of chromatids in each cell.
- The chromosome number does not change from 46 in a diploid cell (2n). However, the number of chromatid changes from 46 to 92 in each cell.
- After interphase stage, two chromatids each is expected to be present in each human cell.
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