The Cell Cycle

Question 1

What is the cell cycle?

Answer 1

The events that take place from one cell division to the next

Question 2

What are the phases that occur in the cell cycle?

Answer 2

1. G1 phase
2. S phase
3. G2 Phase
4. M phase
5. M0 phase - maybe

Question 3

What happens in the G1 phase?

Answer 3

1st growth phase - the cell produces new proteins, grows and carries out its normal tasks for the body

• The enzymes, cytoplasmic organelles and other molecules double in number

Question 4

When does the G1 phase end?

Answer 4

When the cell’s DNA begins to duplicate.

Question 5

What happens in the S phase?

Answer 5

Synthesis phase - the DNA molecule in the cell nucleus form exact copies of themselves.

Question 6

What happens in the G2 phase?

Answer 6

2nd growth phase - involves preparation for cell division including the cell assembling the special structures needed for cell division.

Question 7

What happens in the M phase?

Answer 7

Mitotic phase - the cell divides into two daughter cells.

Question 8

What happens in the G0 phase?

Answer 8

When some cells leave the cycle and stop dividing for days, years or even for the rest of the person’s life.

Question 9

What is mitosis?

Answer 9

The division of the cell’s nucleus in which the two daughter nuclei have the same chromosomes as the parent nucleus; cell division.

Question 10

What are the five stages of mitosis?

Answer 10

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

Question 11

What happens in interphase?

Answer 11

1. The period between nuclear divisions where the cell goes through the phases of the cell cycle.
2. The nucleus is well defined and bounded by the nuclear membrane
3. Outside of the nucleus 2 centrioles organise microtubules into a spindle

Question 12

How much time does the cell spend in interphase?

Answer 12

It accounts for 90% of the cell cycle

Question 13

What happens during prophase?

Answer 13

1. 2 pairs of centrioles become visible early in prophase
2. They move to opposite ends of the cell and microtubules begin to radiate from them
3. Nucleolus disappears and nuclear membrane begins to break down/disappear.
4. Chromatin threads of DNA become tightly coiled and are seen as chromosomes.

Question 14

What does coiling the DNA help it to do?

Answer 14

Coiling the DNA molecules makes it easier to distribute the DNA to the daughter cells.

Question 15

What happens during metaphase?

Answer 15

1. The spindle fibres will push/pull the chromosomes
2. The chromatid pairs line up on the equator of the cell.
3. The centromere of each pair is attached to a spindle fibre.

Question 16

What happens during anaphase?

Answer 16

1. Each pair of chromatids separate at the centromere
2. The spindle fibres contract and the new chromosomes are pulled away from one another towards opposite poles of the cell.

Question 17

What happens during telophase?

Answer 17

1. Two sets of chromosomes form tight groups at each pole of the cell
2. A nuclear membrane forms around each group and nucleolus appears in each new nucleus
3. The spindle fibres disappear, chromosomes gradually uncoil to become chromatin threads
4. The cell begins to pinch

Question 18

What happens during cytokinesis?

Answer 18

1. A furrow develops in the cytoplasm between the 2 nuclei
2. Furrow gradually deepens until it cuts the cytoplasm in two parts, each with own nucleus

Question 19

What does mitosis and cytoplasmic division result in?

Answer 19

Two genetically identical diploid daughter cells