Question

During which phase(s) of the cell cycle, the amount of DNA in a cell remains at 4C level if the initial amount is denoted as 2C?

• A. Only G2
• B. G1 and S
• C. G0 and G1
• D. G2 and M

Answer 1

The correct option is D

G2 and M

The correct option is D.

Explanation for the correct option:

1. At certain points during M-phase, both 4C and 2C DNA is present.
2. The S phase occurs when the amount of DNA in the cell doubles.
3. As a result, the amount of DNA present in the G2 phase is 4C.
4. The cell's contents have been doubled, preparing it for further mitotic division.
5. Interphase is made up of the G1 phase (cell growth), S phase (DNA synthesis), and G2 phase (cell growth).
6. At the completion of the interphase, the mitotic phase begins, which consists of mitosis and cytokinesis and results in the production of two daughter cells.

Explanation for the incorrect option:

Option A:

1. The RNA, proteins and other macromolecules essential for the multiplication of cell organelles, spindle formation, and cell development are created during the G2 phase (Gap 2) as the cell prepares to enter the mitotic phase.
2. The G2 phase is characterized by fast cell growth and protein synthesis as the cell prepares for mitosis.
3. Surprisingly, the G2 phase is not required for all cell types, since some (especially immature Xenopus embryos and certain malignancies) progress directly from DNA replication to mitosis.

Option B:

1. During the G1 phase, the cell physically expands and increases the volume of both protein and organelles.
2. During the S phase, the cell duplicates its nucleosomes and copies its DNA to form two sister chromatids.
3. The G1/S transition is a step in the cell cycle that occurs at the junction of the G1 phase, during which the cell develops, and the S phase, during which DNA is reproduced.

Option C:

1. G0 phase: resting state, also known as the gap phase.
2. Many cells spend the majority of their time in this phase, either resting or executing assigned tasks.
3. Chemotherapy is generally ineffective. G1 phase: gap 1 phase, also known as interphase.

Final answer: G2 and M phase(s) of the cell cycle, the amount of DNA in a cell remains at 4C level if the initial amount is denoted as 2C.