Question

Hello,

please try to answer it as accurate as you can because answer accuracy is the most important.

1_Before a cell undergoes mitotic cell division:

a)what has to happen first, regarding its DNA?

b)If (what you wrote in 2a) didn’t happen, what problem would arise?

2_There are some cells which after they mature (fully differentiate into their specific cell type) never undergo division (such as heart muscle cells) again. These cells are in what phase? _________

3_How are phosphates involved in regulating the activity of a cyclin dependent kinase (Cdks)?

4_ How does cytochrome c initiate apoptosis? What are the roles of Bax and Bak in this initiation? How does Bcl affect apoptosis?

Answer 1

1) Before a cell undergoes mitotic cell division:

a)what has to happen first, regarding its DNA?

Before a cell undergoes mitotic cell division, the strands of DNA must be copied and then checked for errors.

Before cell division, the cell makes a copy of its entire DNA during the S or called as synthesis phase of the cell cycle.

When DNA is copied, means has two copies of each strand, then it is called as chromosomes.

G2 phase is called check point which checks the DNA for errors or check the DNA for any breaks
before initiation of the cell division.

b)If (what you wrote in 2a) didn’t happen, what problem would arise?

If this didn’t happen means DNA replication or check point not occur then cell does or undergo division with mutations or errors.

Replication occurs for cell growth and division. If DNA doesn't do its job then both daughter cells cannot receive a copy of the blueprint, which they need to survive and reproduce.

This G2/M checkpoint is a safety measure for multicellular organisms like animals.

If this didn’t happen then it results in Cancers, death of the entire organism. This is because cells with damaged DNA will reproduce.

2) There are some cells which after they mature (fully differentiate into their specific cell type) never undergo division (such as heart muscle cells) again. These cells are in the g0 phase.

When these cells reach their final mature state, they did not need to divide again and again. So, the cells leave G1 and enter an alternative phase called as G0 phase where they stop dividing permanently.