Week 5_Mitosis

Question 1

what is mitosis?

Answer 1

the process of separating and segregating chromosomes

Question 2

what is DNA like before S-phase?

Answer 2

46, one-chromatid chromosomes

Question 3

what is DNA like after S-phase?

Answer 3

46, two-chromatid chromosomes

Question 4

list the phases of mitosis in order:

Answer 4

PMAT:
- prophase
- metaphase
- anaphase
- telophase

Question 5

what happens during prophase?

Answer 5

(1) chromosomes condense

(2) nuclear membrane breaks down (dissolves)

(3) two spindle poles form and migrate to opposite ends of the cell

(4) a network of microtubules will grow out from the spindle poles

Question 6

what happens during metaphase?

Answer 6

chromosomes line up in the center of the cell

(1) kinetochore microtubules attach to the kinetochore proteins on the centromeres of the chromosomes

(2) kinetochore microtubules move the chromosomes to the metaphase plate (equator of cell, not an actual structure)

Question 7

microtubules are composed of a protein called ___

Answer 7

tubulin

Question 8

each tubulin is made of an ___ and ___ subunit and can ___ to form a microtubule with a hollow core

Answer 8

alpha and beta subunit

polymerize to form a microtubule with a hollow core

Question 9

describe the 2 poles of the spindle pole

Answer 9

(-) end at the spindle pole

microtubules lengthen and shorten from the (+) end

Question 10

what is polymerization?

Answer 10

addition of tubulin proteins which allows microtubules to grow in length on the (+) end

Question 11

what is depolymerization?

Answer 11

loss of tubulin proteins which allows microtubules to shorten in length on the (+) end

Question 12

how do chromosomes remain attached to microtubules as they are polymerizing/depolymerizing?

Answer 12

2 motor proteins, CENP-E and Dynein (located in the kinetochore) move the chromosomes forward and backward as the (+) end grows and shortens

Question 13

what happens during anaphase?

Answer 13

chromatids are separated and segregated

(1) if chromosomes are aligned at the metaphase plate, anaphase promoting complex (APC) is activated

(2) APC will destroy the cohesion proteins holding the sister chromatids together –> separation
- each 2-chromatid chromosome becomes two 1-chromatid chromosomes

(3) chromosomes are segregated to opposite ends of the cell by kinetochore microtubules

Question 14

how has the # of chromosomes in the cell changed as a result of anaphase?

Answer 14

of chromosomes in the cell has doubled

Question 15

what are the types of microtubules involved in mitosis?

Answer 15

polar microtubules

aster microtubules

kinetochore microtubules

Question 16

what do polar microtubules do?

Answer 16

extend from spindle pole to spindle pole

Question 17

what do aster microtubules do?

Answer 17

connect spindle poles to cell membrane

Question 18

what do kinetochore microtubules do?

Answer 18

connect the chromosomes to the spindle poles and segregate the DNA

Question 19

what happens during anaphase A movement?

Answer 19

chromosomes move away from each other (depolymerization of kinetochore microtubules)

Question 20

what happens during anaphase B movement?

Answer 20

spindle poles move away from each other (polymerization of polar microtubules)

Question 21

what happens during telophase?

Answer 21

chromosomes decondense

nuclear membrane reforms around chromosomes

(1) spindle apparatus disassembles

(2) nuclear envelopes form around each set of chromosomes

(3) chromosomes begin to decondense

Question 22

how do chromosomes remain attached to microtubules as they are polymerizing/depolymerizing?

Answer 22

2 motor proteins, CENP-E and Dynein (located in the kinetochore) move the chromosomes forward and backward as the (+) end grows and shortens

Question 23

what happens during anaphase B movement?

Answer 23

spindle poles move away from each other (polymerization of polar microtubules)