2.6.1- The Cell Cycle And Its Regulation

Question 1

Define interphase.

Answer 1

Phase of cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phases.

Question 2

Define ‘mitosis’.

Answer 2

Type of nuclear division that produces daughter cells generically identical to each other and to the parent cell.

Question 3

Define ‘cytokinesis’.

Answer 3

Cytoplasmic division that follows nuclear division, resulting in two new daughter cells.

Question 4

What is apoptosis?

Answer 4

Programmed cell death.

Question 5

What is senescence?

Answer 5

Where the cell can no longer divide.

Question 6

To reproduce cells, what do cells do in simple terms?

Answer 6

They duplicate and split into two daughter cells.

Question 7

Mitosis is a type of _________ _________.

Answer 7

Nuclear division.

Question 8

Mitosis is made up of what two general parts?

Answer 8

Nuclear division and cytokinesis (cytoplasmic division).

Question 9

Between phases of mitosis is what?

Answer 9

Interphase.

Question 10

What is generally happening in interphase as a whole?

Answer 10

Elaborate preparations are born made for cell division- it is a carefully controlled and ordered sequence of events with checkpoints.

Question 11

List in order the stages of the cell cycle.

Answer 11

Gap1- G1 phase 
(GapO- G0 phase)
S Phase- Synthesis 
Gap2- G2 Phase
Mitosis

Question 12

What are the two main checkpoints in the cell cycle, in interphase?

Answer 12

The G1/S phase- also known as the restriction point. G2/M checkpoint.

Question 13

Aside from the two main checkpoints in the cell cycle, what are two other, less dominant checkpoints?

Answer 13

Early G1 and halfway through mitosis.

Question 14

What are the four purposes of the checkpoints in the cell cycle?

Answer 14

• ensure the cell cycle can’t be reversed
• prevent uncontrolled division that could cause tumours
• ensure DNA’s only duplicated once in each cycle
• detect and repair any damage caused to the DNA

Question 15

At the M phase of the cell cycle, list the three events that take place in the cell.

Answer 15

• cell growth stopped
• cytokinesis
• nuclear division that’s split into four stages- prophase/ metaphase/ anaphase/ telophase

Question 16

At the G0 phase of the cell cycle, what are the two events that the place within the cell?

Answer 16

• cells undergo apoptosis/ senescence/ differentiation

* some cells stay in the G0 phase for a v long time or indefinitely- eg neurones

Question 17

List the five events that take place inside the cell at the gap1- G1 phase of the cell cycle.

Answer 17

• organelles duplicate
• cells grow and increase in size
• transcription of genes to make RNA
• P53 tumour suppressor gene controls the phase
• biosynthesis (eg protein synthesis) incl making enzymes needed for DNA replication in the S phase

Question 18

The P53 gene is a ________ _________.

Answer 18

Tumour suppressor.

Question 19

The P53 gene controls which phase of the cell cycle?

Answer 19

The G1 phase.

Question 20

The G1 phase is also known as what?

Answer 20

The growth phase.

Question 21

The synthesis phase is a _______ phase.

Answer 21

Rapid.

Question 22

Explain why the S phase of the cell cycle is a rapid phase.

Answer 22

The DNA bad pairs are more susceptible to mutagenic agents, so the fast speed reduces the chances of spontaneous mutations.

Question 23

What is the event that takes place in the cell during the S Phase of the cell cycle?

Answer 23

*DNA replication

Question 24

Once in the S phase, the cell is committed to what?

Answer 24

Completing the cell cycle.

Question 25

When is the cell committed to completing the cell cycle?

Answer 25

Once it has entered the S phase.

Question 26

In the S phase, explain the result when all the chromosomes are duplicated.

Answer 26

Each duplicated chromosome consists of a pair is identical sister chromatids.

Question 27

What event takes place in the cell at the G2 phase?

Answer 27

The cell grows.

Question 28

In the M phase, what does the checkpoint chemical trigger?

Answer 28

The condensation of the chromatin.

Question 29

Explain the checkpoint that takes place in the M phase of the cell cycle.

Answer 29

Half way through the M phase, the metaphase checkpoint ensures the cell is ready to complete mitosis.

Question 30

Some cells do not have what phase of the cell cycle?

Answer 30

The G0 phase.

Question 31

Give an example of a cell that doesn’t have the G0 phase.

Answer 31

The epithelial cells that line the gut.

Question 32

The G0 phase is a ________ _________.

Answer 32

Resting phase.

Question 33

How does a cell enter the G0 phase?

Answer 33

It is triggered by a checkpoint chemical during early G1 phase at the restriction point.

Question 34

Explain the G1 phases checkpoint function.

Answer 34

The checkpoint control mechanism ensures the cell is ready to enter the S phase of the cell cycle and to begin DNA synthesis.

Question 35

Explain the checkpoint that is in the G2 phase of the cell cycle.

Answer 35

Special chemicals ensure the cell is ready for mitosis by stimulating proteins that will be involved in making the chromosomes condense and the spindles form.

Question 36

Give a reason as to why every DNA molecule is replicated in the S Phase of the cell cycle.

Answer 36

Crates the chromosomes are u would and the DNA Is diffuse.

Question 37

What is a housekeeping gene?

Answer 37

A gene that’s active in all types of cells.

Question 38

In the S phase, there is a specific sequence for the gene replication- explain what that is.

Answer 38

Housekeeping genes are duplicated first and genes that are normally inactive in specific cell types are replicated last.