CH 10.6: Control of the Cell Cycle

Question 1

What are the 2 Irreversible steps of the Cell Cycle?

Answer 1

• DNA replication

- The separation of the sister chromatids during anaphase

Question 2

What is MPF?

Answer 2

• Mitosis Promoting Factor

- Cyclin + cdc2 (Kinase)

Question 3

What are the 2 key aspects of MPF?

Answer 3

• It’s activity follows cyclin activity= Increasing going into mitosis & decreasing coming out
• The enzymic activity of MPF involves the phosphorylation of proteins

Question 4

What is the protein encoded by the cdc2 gene?

Answer 4

-Kinase

Question 5

What role do the cdk Enzymes play?

Answer 5

-They are the engine that drives cell division

Question 6

What are the 3 checkpoints of the Cell Cycle?

Answer 6

• G1/S
• G2/M
• late Metaphase (the spindle checkpoint)

Question 7

What is the purpose of having checkpoints?

Answer 7

• It allows the cycle to be delayed/ halted when necessary (nutrient deficiency or damage detected)
• It assesses internal state & integrates external signals

Question 8

What is the purpose of the G1/S checkpoint?

Answer 8

• AKA Restriction point!
• It is the primary point at which the cell decides to divide or not= external signals can influence events of the cell cycle

Question 9

What is the purpose of the G2/M checkpoint?

Answer 9

• It represents the commitment to Mitosis
• It examines the success of DNA replication & can stop if the replication is wack
• It also examines the balance of kinase that adds inhibitory phosphates w/ the phosphatase that removes them

Question 10

What is the purpose of the late Metaphase checkpoint?

Answer 10

• It is the spindle checkpoint
• Ensures that all the chromosomes are attached to the spindle in preparation for anaphase & making sure that they are arranged on the metaphase plate

Question 11

What is the primary mech of Cell Cycle control?

Answer 11

-Phosphorylation to amino acids serine, threonine, tyrosine in proteins

Question 12

What is APC?

Answer 12

-Anaphase promoting complex

Question 13

What are the 2 main purposes of APC in Mitosis?

Answer 13

• To trigger anaphase itself by
• Activating separase that removes the cohesins holding the sister chromatids together
• Necessary for destruction of mitotic cyclins to drive cells out of mitosis

Question 14

How does APC mark proteins for destruction?

Answer 14

-By the Proteosome= organelle responsible for the controlled degradation of proteins

Question 15

What is the signal to degrade a protein?

Answer 15

• Ubiquitin

- SO APC acts as ubiquitin ligase

Question 16

What are the differences between complex animals & single-celled eukaryotes in terms of cdk & signals acted on the cell?

Answer 16

• Multiple cdks control the cycle vs 1 cdk in yeasts

- Animals cells respond to more external signals vs yeast bc yeasts are horny & only respond to those

Question 17

How are cells able to sense the density of the cell culture around them?

Answer 17

-When cells touch, receptor proteins in plasma membrane activate a signal transduction pathway that acts to inhibit cdk action= prevents entry to cell cycle

Question 18

How do Growth Factors act?

Answer 18

-They trigger intracellular signaling systems

Question 19

What is the passage through the checkpoints controlled by?

Answer 19

-The cdk enzymes

Question 20

If the gene encoding one of the proteins mutated so that it could not perform its normal function, what would be the consequences?

Answer 20

• The chromosomes aren’t able to condense
• The chromosomes would not be able to properly align at the metaphase plate
• Separation of sister chromatids would not likely occur during anaphase A
• The nuclear envelope would not be able to form

Question 21

What is true about Mitosis & Cytokinesis?

Answer 21

-At the end of cytokinesis there are 2 daughter cells w/ a normal complement of diploid genetic material

Question 22

What happens to the microtubules that are attached and unattached to the chromosomes during anaphase?

Answer 22

-The microtubules attached to the chromosomes are gonna shorten while the microtubules that aren’t attached are gonna elongate as the cell expands

Question 23

What happens if Cohesin failed to degrade during metaphase/anaphase transition?

Answer 23

-The daughter cells wouldn’t have a complete set of chromosomes & there would be 2 copies of the chromosomes present

Question 24

What is true about the human somatic cell that is in G2 about their chromosomal number & structure?

Answer 24

• The cells would be considered Haploid, Diploid, Tetraploid

- They would also be aligned in the middle of the cell

Question 25

In what phase is the success of DNA replication examined?

Answer 25

-G2 phase

Question 26

At what phase would the cell w/ a low pH NOT pass the checkpoint?

Answer 26

-G1 phase