Cell Cycle

Question 1

What is the purpose of the cell cycle?

Answer 1

duplication of identical cells; one cell divides into two

Question 2

List 4 reasons why the cell cycle happens

Answer 2

• development: cells duplicate and can then differentiate (become other types of cells)
• wound healing: to replace damaged cells
• replacement of old or damaged cells
• pathological: cancer

Question 3

3 different cell division rates between cell types

Answer 3

Most Neurons-don’t divide
Fibroblasts (part of skin)-can divide every 20 hours
Bone marrow cells-divide every 90.5 hours

Question 4

G1 phase

Answer 4

first growth phase preparing for rest of the cell cycle,
makes sure the cell is big enough, has enough components.
during this phase the chromosomes only have one copy. Two homologous chromosomes one from dad and one from mom

Question 5

G0 phase

Answer 5

cell cycle arrest
some cells can go from G0 into G1 but require an external signal to do so. Other cells never enter G1 because they don’t replicate. And other cells never STOP replicating so they’re NEVER in G0

Question 6

S

Answer 6

duplication of chromosome into sister chromatids. Identical copies of the same chromosomes, held together by centromere

Question 7

G2

Answer 7

synthesis of proteins required for mitosis

Question 8

Interphase includes…

Answer 8

G1, S, G2

Question 9

Mitosis

Answer 9

Is the actual replication of the chromosomes. What I ALWAYS had deemed was the cell cycle. It’s the process by which DNA is divided into 2 identical cells

Question 10

Most cell growth occurs during…

Answer 10

G1 and G2 phases

Question 11

Describe DNA packing during the cell cycle

Answer 11

• DNA has areas that are unwound so that transcription/translation can occur during growth phases
• all the DNA is unwound during S so that the DNA can be replicated
• Compared to mitosis where the DNA is mostly tightly packed

Question 12

G1 checkpoint checks for what 4 things?

Answer 12

• Cell size
• Nutrients
• Growth factors
• DNA damage

Question 13

G2 checkpoint checks for what 3 things?

Answer 13

• cell size-is the cell big enough?
• DNA replication-has it replicated?
• Is the DNA damaged?

Question 14

What’s the most important checkpoint?

Answer 14

G1 TO S

Question 15

How does the cell know that checkpoints have been reached?

Answer 15

• cellular signaling

- regulators of checkpoints

Question 16

What times of cellular signaling helps the cell know the checkpoints have been reached?

Answer 16

External-growth signals that tell the cell to divide

Internal-that checks for things like DNA damage

Question 17

What are the regulators of checkpoints?

Answer 17

Cyclin and CDK

Question 18

Cyclin

Answer 18

protein regulator of CDK

Question 19

CDK

Answer 19

is always present but not active most of the time, only active when cyclin is around, a protein that phosphorylates other proteins

Question 20

Growth factors can stimulate…

Answer 20

the translation/transcription of a cyclin (generally for the G1 to S transition)

Question 21

CDKs can turn cyclins from

Answer 21

inactive to active, and active to inactive

Question 22

when CDKs are no longer needed they are

Answer 22

degraded by protosome

Question 23

Cells said to be in the G0 stage are…

Answer 23

in an extended G1 phase and no longer cycling. They would require an external signal to be an active part of the cell cycle again

Question 24

Cells in the G2 stage of the cell cycle have ____ as cells of the same species in the G1 stage

Answer 24

twice as many chromatids

Question 25

A cell cycle ‘checkpoint’ would be best described as?

Answer 25

specific stages when further progress of the cell cycle can be halted

Question 26

The cell is said to be committed to go through the cell cycle after it passes which of the following checkppoints?

Answer 26

G1 to S. this checkpoint commits the cell to the cell cycle after DNA has been replicated

Question 27

The purpose of a cyclin is to

Answer 27

activate the kinase activity of CDK