Unit 9: Cellular Growth Control

Question 1

What is the cell cycle?

Answer 1

A series of tightly regulated events that include interphase and mitosis in which a cell grows, replicates it’s DNA, and divides into two genetically identical daughter cells.

Question 2

What are the steps of interphase?

Answer 2

G1, S, G2

Question 3

Mitosis occupies a very short cycle in what cell type?

Answer 3

Somatic cells

Question 4

What is the importance of checkpoints in a cell cycle?

Answer 4

They ensure appropriate progression through cell cycle

Question 5

What is the first step in progression of a cell through the cell cycle?

Answer 5

Cyclin-dependent kinases (CDK’s) are activated by binding to cyclin proteins

Question 6

The levels of what proteins oscillate throughout the cell cycle?

Answer 6

Cyclin

Question 7

What cyclin promotes entry into mitosis and how?

Answer 7

Cyclin B binds to CDK1

Question 8

How are CDK fully activated?

Answer 8

By cyclins AND other steps such as phosphorylation by other kinases (CDK activating kinases/ CAKs)

Question 9

What is Proteolysis?

Answer 9

Degradation of specific proteins which regulate cell cycle progression

Question 10

What triggers Proteolysis?

Answer 10

Ubiquitin

Question 11

When a cell is ubiquitinated, what happens?

Answer 11

It is targeted by a proteosome which chews up and degrades proteins.

Question 12

What does the anaphase promoting complex/cyclosome (APC/C) do?

Answer 12

Adds ubiquitin to specific cellular targets.

Question 13

What is another name for Ubiquitin ligase?

Answer 13

Anaphase promoting complex/cyclosome

Question 14

When a cell is ready to leave mitosis, what happens?

Answer 14

M phase cyclins are ubiquitinated and degraded by a proteosome.
When the cyclins are degraded, they can no longer activate M phase CDK’s and dephosphorylate CDK substrates.

Question 15

How were cell cycle genes largely identified?

Answer 15

In budding yeast

Question 16

Why is accurate replication of a genome important for a cell?

Answer 16

Prevents disease

Question 17

What is a situation in which a cell has the wrong number of chromosomes?

Answer 17

Aneuploidy

Question 18

At what step of the cell cycle is the genome copied?

Answer 18

S phase

Question 19

What happens when a genome is copied and is ready to move on to the next step?

Answer 19

The origin of replication bound Origin Recognition complex (ORC) recruits MCM helicase to DNA.

Question 20

What do S phase CDK’s activate?

Answer 20

Activate DNA-bound MCM helicase

Question 21

What does DNA-bound MCM helicase do?

Answer 21

Activates helicase and promotes recruitment of DNA Polymerase

Question 22

What does DNA polymerase do?

Answer 22

Copies DNA

Question 23

When replication begins, what stops any additional rounds of replication from occuring?

Answer 23

The phosphorylation of the ORC which prevents the recruitment of additional MCM helicases

Question 24

When are ORC’s phosphorylated and therefore inactive?

Answer 24

During replication up until mitotic exit when the APC/C inactivates the CDKs (by degrading M phase cyclins)

Question 25

What is chromatin

Answer 25

Mixture of DNA and DNA binding proteins

Question 26

What wraps DNA into a compact structure?

Answer 26

Nucleosomes

Question 27

What links replicated sister chromatids together?

Answer 27

Cohesin

Question 28

How do microtubules connect to the chromosomes?

Answer 28

kinetochores