Mitosis, the cell cycle and cancer

Question 1

What does mitosis produce?

Answer 1

Produces two daughter cells > have the same number of chromosomes as the parent cell and each other

Question 2

What are the different stages of mitosis? (4)

Answer 2

1) Prophase
2) Metaphase
3) anaphase
4) Telophase and cytokinesis
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Question 3

Describe the process of prophase?

Answer 3

Chromosomes first become visible > initially thin threads > later shorten and thicken

1) Controls move to opposite ends (poles) of the cell

2) From each of the centrioles , spindle fibers develop > span cell pole to pole

3) Nucleolus disappears and the nuclear envelope breaks down > leaving the chromosomes free in cytoplasm of cell

4) Chromosomes are drawn towards the equator of the cell by the spindle fibers attached to the centromere

Question 4

Describe the process of metaphase?

Answer 4

Made up of two chromatids > each chromatid is an identical copy of DNA from the parent cell

1) Chromatids are joined by the centromere

2) Some of the chromosomes pulled along the spindle apparatus

3) Arranged across the equator of the cell

Question 5

Describe the process of anaphase?

Answer 5

1) Centromeres divide into two

2) Spindle fibers pull the individual chromatids > making up the chromosomes apart

3) Chromatids move rapidly to respective poles of cell > now referred as chromosomes

REQUIRES ENERGY

Question 6

What happens during interphase?

Answer 6

LONGEST STAGE IN CELL CYCLE

• Replicates DNA to prepare for mitosis

Question 7

Describe the G1 phase of interphase

Answer 7

• Signal is received telling the cell to divide again
• Cells make the RNA, enzymes and other proteins required for growth

Question 8

Describe the S phase of interphase

Answer 8

• The DNA in the nucleus replicates (resulting in each chromosome consisting of two identical sister chromatids)

(SYNTHESIS OF DNA)

Question 9

Describe the process of the G2 stage of interphase

Answer 9

1) Cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired

2) Other preparations for cell division are made

Question 10

Describe the process of telophase

Answer 10

• Chromosomes reach their respective poles and become longer and thinner > disappearing > leaving only wide spread chromatin
• Spindle fibers disintegrate
• Nuclear envelope and nucleolus reform

Question 11

Describe the process of cytokinesis?

Answer 11

• The cytoplasm divides > to reform 2 genetically identical cells
• Physical separation of parent cell into 2 genetically identical daughter cells

Question 12

What is chromatin?

Answer 12

The material that makes up chromosomes, it consists of DNA and the protein histone

Question 13

What is the structure of the spindle fibers?

Answer 13

Protein microtubules

Question 14

What is the function of the spindle fibres?

Answer 14

• Divides the genetic material of a cell > equally divide the chromosomes in a parental cell into two daughter

Question 15

What is a tumour?

Answer 15

A swelling in an organism that is made up of cells that continue to divide in an abnormal way.

Question 16

At one stage does a tumour become cancerous?

Answer 16

When it changes from benign to malignant

Question 17

What is the biological importance of mitosis? (3)

Answer 17

1) Growth > from the point point of fusion from 2 haploid cells > form organism

2) Repair > damaged or dead cells need to be replenished > must have identical structure and function to previous cells

3) Reproduction > single celled organisms divide by mitosis to give 2 new organisms > genetically identical

Question 18

What causes the uncontrollable division of cells?

Answer 18

A mutation in a gene leads to uncontrollable mitosis

Question 19

Describe the treatment of cancer

Answer 19

• Killing dividing cells by blocking part of cell cycle > cell cycle disrupted > cancer growth ceases

1) Preventing DNA from replicating

2) Inhibiting the metaphase stage of mitosis > interfering with spindle formation

Question 20

How do prokaryotic cells divide?

Answer 20

Binary fission

Question 21

Describe the process of binary fission (2)

Answer 21

1) Replication of the circular DNA and of plasmids

2) Division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.

Question 22

Describe how viruses replicate

Answer 22

REQUIRE HOST CELL

1) Attaches to host cell with attachment proteins on host cell surface

2) Inject nucleic acid into host cell > provides instructions for host cell tp start producing viral components (structural proteins)

Question 23

What is mitotic index?

Answer 23

The ratio of the number of cells undergoing mitosis to the total number of cells