The Cell Cycle

Question 1

Roles of Cell division

Answer 1

Reproduction & Growth & Development

Question 2

Prokaryotic cells undergo ______ ________ to divide because ________________________ and the result is _____________.

Answer 2

1. binary fission (NOT mitosis)
2. they are unicellular with a single circular chromosome (simpler than eukaryotes)
3. two genetically identical daughter cells

Question 3

How do eukaryotic cells divide?

Answer 3

Mitosis

Question 4

What is the centromere?

Answer 4

Site of attachment of chromatids and kinetochore

Question 5

Name the four distinct phases of interphase

Answer 5

G1 -> S-phase -> G2 -> M phases

Question 6

What happens during G1

Answer 6

GAP 1

• normal cell activities
• the cell is preparing to divide
• one copy of genome |

Question 7

What happens during S phase

Answer 7

SYNTHESIS PHASE
1 copy of genome -> two copies
| -> |’|

Question 8

What happens during G2

Answer 8

GAP 2
- normal cell activities
BUT cell is now committed to eventual mitosis

Question 9

What happens during M phase

Answer 9

Mitosis (separation of chromatids)

Question 10

Name the six phases of mitosis in order

Answer 10

Prophase -> Prometaphase -> Metaphase -> Anaphase -> Telophase -> Cytokinesis

Question 11

Main process in prophase

Answer 11

Chromosomal condensation

Question 12

How many chromosomes and chromatids are there in prophase

Answer 12

2 chromosomes, 4 chromatids

Question 13

When do the microtubule organizing centers replicate

Answer 13

S phase

Question 14

What happens to the microtubule organizing centers during prophase

Answer 14

They migrate away from the nucleus towards periphery of cell

Question 15

How do microtubules move chromosomes in mitosis

Answer 15

• polymerization/depolymerization
• kinesin (+) end directed motor
• dyenin (DIE = negative) end directed motor

Question 16

Main process of prometaphse

Answer 16

Nuclear envelope breakdown (NEBD), microtubules reach for chromosomes “fishing”

Question 17

Stable attachment occurs when the microtubules attach to:
1.
2.
3.

Answer 17

1. kinetochore
2. other microtubules
3. membrane

Question 18

What happens if the microtubules misses in prometaphase

Answer 18

it depolymerizes

Question 19

Main process of Metaphase

Answer 19

Chromosomes line up at metaphase plate

Question 20

How are chromosomes pushed to the middle in metaphase

Answer 20

Polymerization and kinesin

Question 21

How are chromosomes pulled to the middle in metaphase

Answer 21

Depolymerization and dyenin

Question 22

Main process of Anaphase

Answer 22

Separation of chromatids
|’| -> |’ ‘|
TWO CHROMATIDS BECOME TWO CHROMOSOMES

Question 23

How are chromosomes pulled to opposite poles in anaphase

Answer 23

Depolymerization and dyenin

Question 24

How is the cell elongated in Anaphase

Answer 24

Overlapping microtubules (polar MTs) “pushing elbows out”

Question 25

Main process of Telophase

Answer 25

Nuclear envelope reformation, chromosomal decondensation

“T for tit”

Question 26

Main process of Cytokinesis

Answer 26

Separation of cytoplasm

Question 27

How is the cytoplasm split during Cytokinesis

Answer 27

Microfilaments form cytokinetic furrow/contractile ring, myosin “walks” along MF to constrict flow

Question 28

What are the three checkpoints of the cell cycle

Answer 28

1. Restriction point at G1/S: most important, are there signals/space/nutrients to divide? Once past restriction point, cell fated for division.
2. G2/M checkpoint: is DNA rep complete?
3. Metaphase/Anaphase checkpoint: are all kinetochores attached by MTs?

Question 29

What is cancer

Answer 29

Uncontrolled cell division due to accumulation of mutations

Question 30

The normal function of a tumor suppressor gene is ______________ and if a mutation interferes with this, it will lead to _________________. An example of a TSG is _____.

Answer 30

1. prevent passage through the cell cycle (brake pedal)
2. uncontrolled cell division
3. BRCAI (dysfunctional copy of genes predisposes you to breast cancer)

Question 31

The normal function of a proto-oncogene is to ___________ and a mutation can cause __________.

Answer 31

1. promote the cell cycle (gas pedal)

2. the gene to ignore stop signals (uncontrolled cell divsion)