Chapter 12 - The Cell Cycle

Question 1

What are the phases of Mitosis?

Answer 1

Prophase, Prometaphase, Metaphase, Anaphase, Telophase and Cytokinesis.

Question 2

What happens in Prophase?

Answer 2

• Chromatin becomes more dense forming chromosomes.
• Sister chromatids join at their centromere.
• Mitotic spindles start to form (centrosomes and microtubules)
• Centrosomes start to move to opposite ends of the cell.

Question 3

What happens in Prometaphase?

Answer 3

• Nuclear envelope fragments apart
• The microtubules can now enter into the microtubules
• Chromosomes become more condensed
• The microtubules start to attach to kinetochores
• Nonkinetochore microtubules interact with the microtubules from the opposite side of the cell.

Question 4

What happens in Metaphase?

Answer 4

• Centrosomes are on opposite poles (sides of cell)
• Chromosomes line up on the metaphse plate
• Each sister chromatid’s kinetochore are attached to microtubules

Question 5

What happens in Anaphase?

Answer 5

• Starts when cohesion proteins are cleaved and separate
• Each daughter chromosome moves toward each end with the shortening of the microtubules
• At the end of anaphase, the two ends of the cell have equivalent and complete collections of chromosomes.

Question 6

What happens in Telophase?

Answer 6

• The two daughter nuclei form in the cell
• Chromosomes become less condense
• Spindle microtubules depolymerize

Question 7

What happens in Cytokinesis?

Answer 7

• The cell splits into two new daughter cells

- a cleavage furrow forms

Question 8

What is a centrosome?

Answer 8

a subcellular region containing material that functions throughout the cell cycle to organize the cell’s microtubules. They help in the assembly of spindle microtubules.

Question 9

What is the kinetochore?

Answer 9

A structure that is made up of proteins that attaches to the DNA at the Centromere

Question 10

What is a Centromere?

Answer 10

A centromere is the section of DNA where it is most closely attached to the sister chromatids

Question 11

What are microtubules?

Answer 11

The elongated form of aster that come out of the Centrosomes. They bind to the chromosomes and pull them apart.

Question 12

What are asters?

Answer 12

a radial array of short microtubules, extends from each centrosome.

Question 13

What does the spindle include?

Answer 13

The spindle includes the centrosomes, the spindle microtubules, and the asters.

Question 14

What are the phases of the Cell Cycle?

Answer 14

Mitotic phase
   - Mitosis
   - Cytokinesis
Interphase (90% of Cell cycle)
   - G1 phase
   - S phase
   - G2 phase

Question 15

What are check points?

Answer 15

Checkpoints are a control point in cell cycle where stop and go-ahead signals can regulate the cycle.

Question 16

What is the importance of cyclins in the cell cycle?

Answer 16

Many of the kinases that drive the cell cycle are actually present at a constant concentration in the growing cell, but they are in an inactive form. Cyclins will activate these kinases.

Question 17

Why are the kinases in the cell cycle called cyclin-dependent kinases?

Answer 17

Because the kinases in the cell cycle cannot be activated without the cyclin.

Question 18

What is MPF?

Answer 18

MPF stands for “Maturation-promoting factor”. MPF causes the cell to start mitosis.

Question 19

What happens when there is no signal at the G1 phase?

Answer 19

The cell will go into G0 phase which is a non-dividing state - Most of the human cells are in G0 phase.

Question 20

Why are cancer cells so dangerous?

Answer 20

Because cancer cells do not need normal signals to divide.

• Normal cells will stop when the cells touching each other and when there isnt enough room for more. Cancer cells will keep mulitpling no matter how tight it is.
• Normal cells divide 20 to 50 times and then die but cancer cells keep dividing and do not die.