Multiple Choice
Checkpoints within the cell cycle:
11. Cell Division
Cell Cycle Regulation
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When a cell in S phase is fused with a cell in G1, __________.
A
the replication of DNA occurring in the original S nucleus is terminated
B
the two nuclei fuse and additional division is arrested
C
the chromosomes of the original G1 nucleus condense in preparation for mitosis
D
the original G1 cell will divide immediately
E
DNA synthesis begins immediately in the original G1 nucleus
Verified step by step guidance1
Understand the cell cycle phases: G1 is the first gap phase where the cell grows and prepares for DNA replication. S phase is where DNA replication occurs. G2 is the second gap phase, and M phase is mitosis.
Recognize that cell fusion experiments help us understand cell cycle regulation. When two cells at different stages of the cell cycle are fused, the cytoplasmic factors from one cell can influence the other.
In this scenario, a cell in S phase is fused with a cell in G1 phase. The S phase cell contains factors that promote DNA replication.
These S phase factors can induce the G1 nucleus to begin DNA synthesis prematurely, even though it hasn't naturally progressed to the S phase.
Therefore, when a G1 cell is fused with an S phase cell, the G1 nucleus is exposed to S phase promoting factors, leading to the initiation of DNA synthesis in the G1 nucleus.
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Cell Cycle Regulation practice set
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