Question

For this question, you will create a drawing that you should upload as an image. (1 bonus point will be awarded for neat and clear images that do not show more than the requested information.) Imagine a haploid eukaryotic cell with a genome consisting of two unique chromosomes. The cell enters the cell cycle and divides by mitosis. Its daughters also enter the cell cycle and divide by mitosis to create granddaughter cells.

1) Draw the original cell in the G1 phase of the cell cycle as a circle with the chromosomes represented as double-stranded DNA molecules.

2) Below the first cell, draw all the daughter cells in G2 phase of their cell cycle using the same representation.

3) Below the daughter cells, draw all the granddaughter cells in G1 phase of their cell cycle.

4) Write the combined total number of chromatids that will be present in both daughters when they are at the beginning of M phase next to your picture of the daughter cells.

5) Could one or more of the granddaughter cells contain an entire DNA strand that was present in the G1 phase of the cell that you drew for (1)? (Not a copy of the strand, but the actual molecule.) Write your one-word answer next to the granddaughter cells.

6) Highlight or label your diagram to justify your answer to (5).

Answer 1

We need the following prior knowledge to answer these questions:

1. Before mitotic phase:

Cell cycle interphase	DNA copy number
G1	n
S	2n
G2	2n

2. Any chromosomal locus exchange by crossing over happens in meiosis, not mitosis.

3. DNA replication is semi-conservative. One DNA strand of the two strands get separated and become the template to synthesise the daughter strand. This complete DNA molecule (one parent strand+one daughter strand) transfers to the daughter cell post mitotic phase.