The cell cycle (mitosis)

Question 1

What occurs during Metaphase?

Answer 1

chromosomes line up at the equator of the spindle (and cell)

Question 2

Name the phase during which DNA and organelles are replication occurs.

Answer 2

interphase

Question 3

Describe and explain what a cancer drug may do to kill or supress cancer cells

Answer 3

1. damage the cells so longer time to recover;
2. reduced rate of mitosis
3. increased doubling time;

Question 4

Explain why meiosis is important in sexual reproduction

Answer 4

produces haploid cells (chromosome number halved) for fertilisation;
maintains the diploid number in next generation;

Question 5

Describe what happens in anaphase

Answer 5

identical chromatids move to opposite poles

Question 6

Other than DNA and organelles increasing, what other PROSSES need to INCREASE for mitosis to occur?

Answer 6

1 of:

• ATP production
• protein synthesis
• replication of centrioles

Question 7

Describe the role of the spindle during mitosis.

Answer 7

they attach to the centromeres (of the chromosomes) and separate chromatids to the opposite poles of the cell

Question 8

Describe and explain how the structure of DNA results in accurate replication.

Answer 8

1. made up of two strands therefore semi-conservative replication is possible;
2. hydrogen bonds holds strands together
3. hydrogen bonds are easily broken so allow strands to separate;
4. base is sequence exposed so it acts as a template so can be copied;
5. complementary base copying occurs as;
6. so the DNA is one sense and one new strand;

Question 9

Describe the behaviour of chromosomes during mitosis and explain how this results in the
production of two genetically identical cells.

Answer 9

1.chromosomes condense.
2.chromosomes are each identical copies due to replication;
3.chromatids move to equator of the cell;
4. and attach to individual spindle fibres;
5.spindle fibres attach to the centromeres and divide the chromosomes into chromotids;
6.chromatids move to opposite poles of the cell;
7.each pole receives
identical copies of each chromosome;
8.nuclear envelope forms around each group of
chromatids

Question 10

Drugs are being developed which only kill cells in a
low oxygen environment. Suggest how these drugs could be useful in the treatment of
cancer.

Answer 10

cancer cells killed, normal body cells survive;

cancer cells low oxygen (as blood supply cannot satisfy demand);

Question 11

Explain the

advantage of cells completing the cell cycle in a short time.

Answer 11

replace cells quickly

Question 12

Mikanolide is a drug that inhibits the enzyme DNA polymerase. Explain why this drug may
be effective against some types of cancer.

Answer 12

Prevents DNA replication as nucleotides of new strand are not joined
as sugar-phosphate bonds are not formed;
therefore Prevents mitosis;

Question 13

If the DNA of the cell is damaged, a protein called p53 stops the cell cycle.
Mutation in the gene for p53 could cause cancer to develop. Explain how.

Answer 13

Cancer cells often have damaged DNA;
p53 is therefore not made;
Cell with faulty DNA divides;
Uncontrolled division produces cancer;

Question 14

Describe the stages of mitosis

Answer 14

1. S(ynthesis)-phase (interphase) - DNA replication occurs
2. Prophase - Chromosomes condense and shorten and become visible
3. Metaphase - chromosomes align at the equator of the cell
4. Anaphase - spindle fibres attach to the centromere of the chromosome and pull each chromatid to opposite pole of the cell
5. Telophase - nuclear envelope re-forms at the groups of the chromatid at each pole of the cell

Question 15

What happens in G1 (first growth) stage?

Answer 15

1. when the proteins from which cell organelles are synthesized are produced

Question 16

What happens in the S (synthesis) phase?

Answer 16

DNA is replicated

Question 17

What happens in G2 (second growth) stage?

Answer 17

when organelles grow and divide and energy stores are increased

Question 18

What happens in nuclear division?

Answer 18

the nucleus divides either into two or four

Question 19

What happens in cell division?

Answer 19

when the whole cell divides into two or four

Question 20

What is cancer?

Answer 20

a group of diseases caused by a growth disorder of cells

Question 21

How do cancer drugs disrupt the fell cycle?

Answer 21

1. preventing DNA from replicating e.g. cisplatin

2. inhibiting the metaphase stage of mitosis by interfering with spindle formation e.g. vinca alkaloids

Question 22

Why are cancer drugs more effective killing cancer cells than normal body cells (apart from hair)

Answer 22

1. The drugs are more effective against rapidly dividing cells
2. as cancer cells divide at a fast rate, they are damaged to a greater degree than normal cells
3. hair cells divide rapidly also, which are targeted by cancer drugs which explains the hair loss in cancer patients-

Question 23

Descibe how the quantity of DNA in cells is increased during phase S.

Answer 23

1. DNA unravels to form two single stranded DNA molecules;
2. these attract complementary nucleotides;
3. these join to sense strands forming daughter DNA.
4. Under the influence of DNA polymerase;
5. bases join by hydrogen bonds between complementary pairs
6. and adjacent sugars join by phosphate bridges;

Question 24

How is the quantity of DNA returned?

Answer 24

1. chromatids separate to poles;
2. during anaphase;
3. nuclear membranes then reform around two daughter nuclei;
4. each containing the diploid number of chromosomes;

Question 25

What is male chromosomes in terms of X AND Y’S

Answer 25

XY

Question 26

What is female chromosomes in terms of X AND Y’S

Answer 26

XX

Question 27

Explain how you could have recognised which cells were in interphase when looking at tissue samples.

Answer 27

1. no visible chromosomes

2. visible nucleus