Question

A plant cell has 12 chromosomes at the end of mitosis. How many chromosomes would it have in the G2 phase of its next cell cycle?
A) 24
B) 12
C) 8
D) 6

Answer 1

Hint: The number of chromosomes remains the same in mitosis. The cell enters the second growth phase, the cell has completed the synthesis phase and the DNA has been duplicated to form sister chromatids and the number remains the same in the next cycle too.

Complete answer: Mitosis is a part of the cell division where there is a duplication of DNA but the number of chromosomes remains the same in the daughter cells. It is also known as reductional division. It includes division of chromosomes equally in both cells and the number of chromosomes remains the same in both the daughter cells. The cell cycle has interphase and the mitotic phase. The mitotic phase has four phases: prophase, metaphase, anaphase and telophase. The interphase has three stages: a first growth phase, synthesis phase and second growth phase. Synthesis phase has duplication of DNA or chromosomes. The sister chromatids are formed for each chromosome and still, the total chromosome number does not change. The second growth phase is also known as the pre mitotic gap phase. The synthesis of spindle fibres takes place and cell prepares for the mitosis. Duplication of the organelles also takes place. Thus at the end of the premitotic gap phase or second growth phase, the number of chromosomes remains 12 but has 24 sister chromatids before the mitosis.
Hence, the correct answer is option B.

Note: The meiosis includes equational division unlike mitosis. The number of chromosomes is halved in meiosis and the same number of chromosomes is found in mitosis. There is a duplication of DNA in both the cell divisions. It is just that the chromosome number remains the same in mitosis after cell division.