19. The cell cycle

Question 1

Name the stages of the cell cycle? (5pts)

Answer 1

1. G1 phase
2. S phase
3. G2 phase
4. M phase
5. Cell cycle restarts

Question 2

Describe the stages of the cell cycle? (5pts)

Answer 2

1. G1 phase- Growth and preparation for the s phase.
2. S phase- DNA synthesis.
3. DNA on chromosomes is duplicated in DNA replication.
4. By the end all the chromosomes contained within the nucleus have been copied.
5. G2 Phase- Growth and preparation for M phase. Increase cytoplasm and number of organelles.
6. M phase- Mitosis and cytokines. Division phase where division of the nucleus , cytoplasm and cell occurs
7. Cell cycle restarts to produce more cells.

Question 3

Describe the G0 Phase? (3pts)

Answer 3

1. G0 Phase= resting phase where no cell division takes place.
2. Many cells in our body are in the G0 phase and not all can re-enter the cell cycle.
3. Liver cells are maintained in the G0 phase unless stimulated to divide.

Question 4

Name the stages of Mitosis? (5pts)

Answer 4

1. Prophase
2. Promethaphase
3. Metaphase
4. Anaphase
5. Telophase

PPMAT

Question 5

Describe the stages of Mitosis? (6pts)

Answer 5

1. Prophase
2. Chromosomes condense
3. Centrosomes move to opposite poles
4. Mitotic spindle forms
5. Pro-metaphase
6. Breakdown of nuclear envelope
7. Chromosomes attach to mitotic spindle
8. Metaphase
9. Centrosome are at opposite poles
10. Chromosomes are at their most condensed and line up at equator of the mitotic spindle
11. Anaphase
12. Sister chromatids separate
13. Each new daughter chromosomes moving to the opposite spindle pole.
14. Telophase
15. Chromosome arrives at the spindle poles
16. Chromosomes decondense
17. Nuclear envelope reforms
18. Cytokines
19. Cytoplasm divides

Question 6

Describe the mitotic spindle? (5pts)

Answer 6

1. Mitotic spindle starts to assemble during Prophase from the centrosomes.
2. The function is to separate the duplicated chromosomes.
3. Constructed from microtubules
4. There are 3 types of microtubules- astral microtubules, kinetochore microtubules and interpolar microtubules.
5. Chromosomes attach to the spindle via the kinetochore.

Question 7

Describe the Astral microtubule?

Answer 7

Projecting out from the poles. Have a role in the orientation and positioning of the spindle within the cell.

Question 8

Describe the Kinetochore microtubules?

Answer 8

Make contact with the kinetochore

Question 9

Describe the interloper microtubules?

Answer 9

Extend from the poles. Do not make contact with the kinetochore.

Question 10

Describe a Kinetochore?

Answer 10

Kinetochore is made up of an inner plate and outer plate. A big macromolecular complex with many different proteins within it which work together.

Question 11

Describe a Fibrous Corona

Answer 11

Assembly of many proteins. Need to be dissembled before anaphase.

Question 12

Describe the Centrosome cycle? (4pts)

Answer 12

1. Microtubule-organising centre in animal cells.
2. Centrosome consists of a pair of centrioles surrounded by pericentriolar material.
3. Duplicated during interphase
4. Migrate to opposite poles in preparation for the M phase.

Question 13

Describe cytokenisis (2pts)

Answer 13

1. Cytokensis is when a contractile ring which is a cytoskeleton structure composed of actin and myosin divides the cell into two.
2. Accumulates between the poles of the mitotic spindle between the plasma membrane.

Question 14

Describe cell organelle division?

Answer 14

All cell organelles must be redistributed between the 2 new daughter cells. Cell organelles cannot spontaneously regenerate so must be present in the new daughter cells.

Question 15

Describe Meisosis? (4pts)

Answer 15

1. Meiosis produces gamets
2. Begins with one diploid cell and ends with 4 haploid cells after 2 rounds of cell division.
   3.
3. In meiosis I homologous chromosomes line up on the spindle and separate to opposite spindle poles
4. In Meiosis II sister chromatids line up on the spindle and separate to opposite spindle poles.
5. Recombination occurs between homologous chromosomes.

Question 16

Describe Meisosis? (4pts)

Answer 16

1. Meiosis produces gamets
2. Begins with one diploid cell and ends with 4 haploid cells after 2 rounds of cell division.
   3.
3. In meiosis I homologous chromosomes line up on the spindle and separate to opposite spindle poles
4. In Meiosis II sister chromatids line up on the spindle and separate to opposite spindle poles.
5. Recombination occurs between homologous chromosomes.

Question 17

Describe Mitosis? (5pts) PPMAT

Answer 17

1. Produces 2 cells
2. 1 round of cell division
3. Diploid cells produced
4. No recombination
5. Growth and repair

Question 18

Describe Meoisis? (5pts)

Answer 18

1. 4 cells
2. 2 rounds of cell division
3. Haploid cells produced
4. Recombination
5. Produces gamets

Question 19

Describe nondisjuction?

Answer 19

Nondisjuctnion is when meiosis goes wrong and it is the failure of homologues to separate from one another either at meiotic division I or meiotic division II.

Question 20

Describe autosomes nondisjuction?

Answer 20

usually fatal due to numerous genes

Question 21

Describe the control of the cell cycle? (4pts)

Answer 21

1. Entry into the cell cycle must be strictly controlled
2. Each phase must only occur once per cell cycle.
3. Phases must be in the correct order- G1, S, G2 and M phase.
4. Phases must be non-overlapping.

Question 22

Describe checkpoints in the cell cycle? (3pts)

Answer 22

1. G1 checkpoint

• checks DNA for damage
• check the extracellular environment for signals

2. G2 checkpoint

• check DNA damage
• check DNA is replicated

3. Metaphase checkpoint
   - ensure all chromosomes aligned on the mitotic spindle.

Question 23

Name cell cycle regulators?

Answer 23

1. Cdks- cyclin dependant kinases

2. Cyclins

Question 24

Describe Cdks? (7pt)

Answer 24

1. Cdk is only active when bound to a cyclin
2. Cdk’s function is to phosphorylate target proteins
3. CDK levels are fairly stable throughout the cell cycle
4. Cyclin levels vary as part of the cell cycle
5. Cdk activation triggers the next step in the cell cycle such as entry into the S phase, M phase.
6. Cyclin degradation terminates Cdk activity.
7. CDK does not change, it is cyclin which fluctuates according to the cell cycle.

Question 25

Describe cyclin?

Answer 25

Different cyclins are produced at each phase of the cell cycle and it is a cell cycle regulator.

Question 26

Describe Neoplasia?

Answer 26

Neoplasia is uncoordinated cell growth. In Neoplasia cells escape normal cell cycle regulation as there are no barriers to prevent uncontrolled progression through the cell cycle.