Lecture 2- Cell division and apoptosis

Question 1

Where does cell division take place?

Answer 1

-Development -Growth -Repair and maintenance -Cell diseases -Reproduction

Question 2

What must happen before a cell divide?

Answer 2

1-There must be a reproductive signal 2-There must be growth (the cell double in size) 3-Replication of DNA 4-Chromosome segregation

Question 3

What is cell cycle?

Answer 3

The period between cell divisions

Question 4

What are the two main components of cell cycle?

Answer 4

Interphase and mitosis/cytokinesis

Question 5

In which phase does the majority of cells spends their time?

Answer 5

Interphase

Question 6

What are the three phases in interphase?

Answer 6

G1, S and G2

Question 7

Describe G1 phase

Answer 7

In G1 the cell double in size and prepare for DNA replication.

Question 8

How many chromatid there are in the chromosome in G1 phase?

Answer 8

In G1 phase there’s only one chromatid per chromosome.

Question 9

What is nuclear envelope?

Answer 9

The double membrane that separates the nuclear content from the cytoplasm.

Question 10

What are Microtubules?

Answer 10

Dynamic scaffolding poles that form the cytoskeleton and the mitotic spindle.

Question 11

Which are the two kind of microtubules in the mitotic spindle?

Answer 11

1-Polar Microtubules 2-Kinetochore Microtubules

Question 12

Describe polar microtubules:

Answer 12

Polar Microtubules form the framework of the spindle and run from one pole to the other.

Question 13

Describe kinetochore microtubules:

Answer 13

Kinetochore microtubules attach to the kinetochore of the chromosomes.

Question 14

What is a centrosome?

Answer 14

Centrosomes are organelles located near the nucleus that orientate the spindle apparatus in the right direction.

Question 15

What’s the function of Restriction?

Answer 15

To activate or arrest the cell cycle. The cell can only progress to the S phase if it has sufficiently grown during the G1 phase.

Question 16

Describe how the activation/arrest of the cell cycle works at checkpoints:

Answer 16

The cell cycle is controller by CDKs. CDKs phosprylate RB in order to inactivate it. Inactivated RB allows the cell cycle to proceeds.

Question 17

Why are cyclins important?

Answer 17

Cyclin phosphorylate CDK so that CDK can phosphorylate RB.

Question 18

Describe S phase

Answer 18

In S phase the DNA Replication begins. Each chromosome starts duplicating from many origins of duplication located along its structure. Centrosomes duplicates as well.

Question 19

How are sister chromatids held together?

Answer 19

Sister chromatids are held together by a protein called cohesin.

Question 20

Describe G2 phase:

Answer 20

In G2 phase the cell prepare for mitosis and duplicates its organelles. Centrosome diverge to opposite ends of the cell.

Question 21

What happens at G2/M transition?

Answer 21

At G2/M transition the two centrosomes separate from each other, their position will determine the spatial disposition of the daughter cells.

Question 22

Describe what happens during Mitosis?

Answer 22

During mitosis a single nucleus give rise to two genetically-identical nuclei.

Question 23

How do the chromosomes appear throughout interphase?

Answer 23

They appear as their uncondensed state called chromatin which looks like yarn in a ball of yarn.

Question 24

Where do microtubules originate and extend from?

Answer 24

Microtubules extend from MTOC (Microtubules organizing centre).

Question 25

Name the five stages of the M phase in the correct order.

Answer 25

Prophase Metaphase Anaphase Telophase Cytokinesis

Question 26

Describe prophase:

Answer 26

The chromatin starts to condense. Th chromosomes are becoming visible, shorter and thicker. Coesin is partially removed. Nuclea envelope breaks down. Kinetochores MT connect kinetochores to centrosomes.

Question 27

Describe metaphase:

Answer 27

Chromatin is fully condensed and visible as separate elements. The chromosomes are moved by the MT mitotic spindle to the metaphase plate.

Question 28

Describe anaphase:

Answer 28

Sister chromatids are segregate to the opposite pole of the cell. Coesin is hydrolized by separase.

Question 29

Where does the energy that moves the daughter chromosomes comes from?

Answer 29

75% comes from the hydrolisation of ATP made by cytoplasmic dynein located in the kinetochores. 25% comes from the shorten of kinetochores microtubules from the poles.

Question 30

Describe telophase:

Answer 30

The two separate bundle of chromatids begin to decondense. Centrosomes nucleated MT asters. Mitotic spinde disappear. Two nuclear envelopes form around the chromosomes.

Question 31

What's cytokinesis?

Answer 31

After chromosome have been segregated and organelles have been distributed the cell split apart.

Question 32

Describe cytokinesis in animal cells:

Answer 32

In animals cells a contractile ring forms on the equatorial plane and pinch off to form two daughter cells.

Question 33

Describe cytokinesis in plant cells:

Answer 33

Since plant cells have a rigid cell wall a septum grwos down along the equatorial plane to form form two daughter cells.

Question 34

What are the three main checkpoints in the cell cycle?

Answer 34

1) Restriction point (G1) 2) G2 phase 3) M checkpoint

Question 35

Describe G2 checkpoint:

Answer 35

G2 checkpoint - this one occurs at the end of G2 and it checks to see if DNA replication has been completed.

Question 36

Describe M checkpoint:

Answer 36

It occurs at the end of metaphase. It checks to see whether the chromatids are arranged correctly on the metaphase plate ensuring that each daughter cell receives the same number of chromosomes before anaphase.

Question 37

What are CDKs and what do CDKs do?

Answer 37

CDKs stand for cyclin-dependent kinases. CDKs phosphorylate RBs, helping the cell to progress to the next stages of the cell cycle.

Question 38

What happens when DNA is damaged during a stage in the cell cycle?

Answer 38

DNA damage triggers the activation of several proteins that can stimulate DNA repair, arrest the cell cycle or induce the cell to undergo apoptosis.

Question 39

Give a brief description of binary fission:

Answer 39

1-The cell increases in size. 2-DNA replication occurs 3-Cytoplasm and nuclei separate to form two new cells.

Question 40

Name common external factors that act as reproductive signals in prokaryotes.

Answer 40

Environmental factors and nutrient factors.

Question 41

What is apoptosis?

Answer 41

Programmed cell death