Meiosis is a key process of eukaryotic cell division that produces haploid gametes from diploid germ-line cells. In a laboratory study of spermatogenesis in a mammalian model organism, the mean mass of DNA per cell was recorded at different stages over a 14-hour period.
The graph below shows the variation in the mean mass of DNA per cell (measured in picograms, pg) before, during, and after the meiotic divisions.
Use the graph to answer the following questions:
During which time interval is the DNA in the chromosomes being copied?
State the two specific times at which a cell division event occurs.
Determine the mean mass of DNA (in pg) in a completed gamete.
Calculate the expected mean mass of DNA (in pg) in a zygote formed by the fusion of two of these gametes.