The amount of DNA per cell of a particular species is measur

The amount of DNA per cell of a particular species is measured in cells found at various stages of meiosis and the cell cycle, and the following amounts are obtained: 3.7 pg, 7.4 pg, and 14.6 pg. Cells that contain 3.7 pg of DNA are likely found in which of the following stages? G1 G2 Prophase I Following telophase II and cytokinesis Anaphase I The amount of DNA per cell of a particular species is measured in cells found at various stages of meiosis and the cell cycle, and the following amounts are obtained: 3.7 pg, 7.4 pg, and 14.8 pg. Cells that contain 7.4 pg of DNA are likely found in which of the following stages? G1 G2 Prophase I Following telophase II and cytokinesis Anaphase I

Solution

After the completion of replication and prior to cytokinesis, a cell will have double the amount of DNA. Suppose a normal cell had X pg of DNA in its resting/G0 phase, then at the end of replication and before cytokinesis it will have 2X pg of DNA. The contents of the cells are halved at the end of meiosis I, therefore now, each cell would again have X pg of DNA (2X/2= X). However at the end of meiosis II, a single cell would have divided to 4 cells, hence each cell will contain X/2 pg of DNA.

At G1 phase, no replication of DNA occurs. Therefore the amount of DNA at this phase would be normal. Hence the phase with 7.4 pg of DNA would be the G1 phase.

At G2 phase, the amount of DNA is double as it occurrs right after the S pahse. Hence, this phase will have 14.8 pg of DNA.

At Prophase I, the amount of DNA is double the normal amount since cytokinesis has not yet occurred. Therefore, this phase too will have 14.8 pg of DNA.

Following Telophase II and cytokinesis, each cell would have been divided into 4 cells. So each cell will only contain X/2 pg of DNA. Hence, the cells at this phase will have 3.7 pg of DNA.

At Anaphase I, the amount of DNA is double the normal amount since cytokinesis has not yet occurred. Therefore, this phase too will have 14.8 pg of DNA.