Cell Division

Question 1

What happens in the G1, S, and G2 phases of cell replication?

Answer 1

G1- preparation to replicate DNA
S- (synthesis) replication of DNA and centrosomes
G2- continues to grow to prepare for division

Interphase- chromatin is threadlike and not condensed

Question 2

What checkpoints are there?

Answer 2

G1 check- from G1 to S
G2 check- from G2 to mitosis
Mspindle check

Question 3

What is the cleavage furrow made of?

Answer 3

Actin and myosin micro filaments

Question 4

What prohibits cell growth?

Answer 4

Density dependent inhibition/contact inhibition and anchorage dependence

Question 5

Describe prophase 1

Answer 5

Homologous chromosomes line up along the metaphase plate and form a synaptonemal complex through the process of synapsis. The pair of chromosomes is called a tetrad. The region of crossing over is the chiasmata.

Question 6

What is the independent assortment of chromosomes?

Answer 6

In metaphase 1, homologous chromosomes can line up in1 of 2 ways. Thus there is 50% chance that the gamete will receive a maternal chromosome and a 50% chance of receiving a paternal chromosome. There is thus 8 million possible numbers of combinations of maternal and paternal chromosomes.

Question 7

What two important factors limit cell size and promote cell division?

Answer 7

The ratio of volume to surface area and the capability of the nucleus to control the cell.

Question 8

What is the significance of crossover?

Answer 8

Produces recombinant chromosomes that combine genes from the mother and father.

Question 9

Describe cell division checkpoints.

Answer 9

Cell division checkpoints are monitored by cyclin dependent kinases. When a kinase binds to its specific cyclin protein, it’s active site is exposed and the molecule is activated. This kinase then catalyzes the phosphorylation of target proteins that regulate the cell cycle.

Growth factor➡️cyclin synthesis➡️CDK Activation➡️cell cycle events