Question

The DNA content of a diploid cell in the G1 phase of the cell cycle is measured. If this DNA content is X, then the DNA content of the same cell at metaphase of meiosis I would be ________.

• A. 0.5 X
• B. 0.5 X
• C. X
• D. 2 X

Answer 1

The correct option is D 2 X

$\bullet$ G1 phase corresponds to the interval between mitosis and initiation of DNA replication. It is the longest phase and is the period of maximum growth of the cell. During this phase the cell grows in size and there is an active synthesis of RNA and proteins. However there is no change in the DNA content of the cell during this phase.
$\bullet$ It is during the S-phase when the DNA content doubles (X becomes 2 X).
$\bullet$ As the cell enters the meiosis-I stage, during prophase it undergoes crossing over.
$\bullet$ During metaphase-I the bivalents become attached to the spindle at the centromere and arrange themselves at the equator of the spindle.
$\bullet$ During anaphase-1 the two chromosomes of each bivalents separate from one another and move to the opposite pole of the spindle. After anaphase-1 each pole has a haploid number of chromosomes. Thus, the DNA content of the cell will be 2 X at metaphase-1.