If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I will be a. 0.25x. b. 0.5x. c. x. d. 2x.

Verified step by step guidance

1. Understand the cell cycle and meiosis: In the G1 phase of the cell cycle, a diploid cell has a complete set of chromosomes, each consisting of one DNA molecule. This is represented as x.
2. Recognize that DNA replication occurs during the S phase, which follows the G1 phase. After the S phase, each chromosome consists of two sister chromatids, each containing one DNA molecule. Therefore, the DNA content doubles to 2x.
3. Identify that meiosis I follows after the S phase. During meiosis I, the cell undergoes one round of division. However, the DNA content per cell does not change during the transition from the S phase to metaphase of meiosis I.
4. Understand that in metaphase of meiosis I, the chromosomes align at the metaphase plate, but the sister chromatids do not separate. This means each chromosome still consists of two chromatids, maintaining the DNA content at 2x.
5. Conclude that the DNA content of the same cell at metaphase of meiosis I is 2x, as the DNA was doubled during the S phase and has not yet been reduced by separation of sister chromatids or subsequent cell divisions.

Key Concepts

Cell Cycle Stages

The cell cycle consists of several phases, including G1, S, G2, and M. In the G1 phase, the cell is preparing for DNA replication, and its DNA content is at its diploid state (x). During the S phase, DNA is replicated, resulting in a diploid cell with double the DNA content (2x) by the end of G2, before it enters mitosis or meiosis.

Meiosis

Meiosis is a specialized form of cell division that reduces the chromosome number by half, resulting in four haploid cells from one diploid cell. During meiosis I, homologous chromosomes are separated, and the DNA content of the cells is halved. Therefore, if the original diploid cell had a DNA content of x, after meiosis I, each daughter cell will have a DNA content of 0.5x.

Metaphase of Meiosis I

Metaphase I of meiosis is characterized by the alignment of homologous chromosome pairs at the cell's equatorial plane. At this stage, the DNA content of the cell is still at the diploid level (2x) because the chromosomes have been replicated during the S phase. However, after the separation of homologous chromosomes in anaphase I, the resulting cells will have a haploid DNA content of 0.5x.