Chapter 6: Cell Division

Question 1

cell cycle

Answer 1

G1 - S - G2 - M

G1 phase:

• cell grow
• produce cell components
• synthesise protein
• chromosome in form of chromatin

S phase:

• synthesise and replicate DNA in nucleus
• chromosome multiples into two identical chromosomes (sister chromatids)
• joined by centromere

G2 phase:

• continue to grow and remain active metabolically
• gather energy
• make final arrangement

M phase:

• mitosis
• cytokinesis

Question 2

Mitosis

Answer 2

Prophase - Metaphase - Anaphase - Telophase

Prophase:

• chromatin is shorted and thicken to form visible chromosomal structure
• nucleus membrane disintegrate
• nucleolus disappear
• centriole move to the opposite poles
• spindle fibre formed

Metaphase:
- sister chromatid is arranged in a single row on the equatorial plane

Anaphase:

• centromere divide into two
• chromosome is separated
• spindle fibre shorten and contract
• sister chromatids are attracted to the opposite poles of the cell

Telophase:

• chromatids at the opposite poles, called sister chromatids
• spindle fibre disappear
• nucleus membrane and nucleus reformed

Question 3

cytokinesis in animal cells

Answer 3

• plasma membrane constrict at the middle of the cell
• microfilaments contract
• cleavage furrow occurs
• cell is split into two daughter cells

Question 4

cytokinesis in plant cells

Answer 4

• vesicle form and combine to form a new cell plate at the centre of cell
• cell plate surrounded by new plasma membrane
• new cell wall substance is formed among the space between cell plate
• cell plate expand outward
• combine with plasma membranes
• cellulose fibre produced to strengthen the new cell wall
• two daughter cells is formed

Question 5

mitosis involve in hydra

Answer 5

form new buds

- to produce new individuals

Question 6

mitosis involve in lizard

Answer 6

• regeneration

- grow new tail if the tail is break

Question 7

uses of stem cell therapy

Answer 7

• to repair damaged cartilage

Question 8

meiosis

Answer 8

prophase 1:

• chromatid shorten and thicken to form visible chromosomal structure
• pairing of homologous chromosomes form bivalent (tetrad)
• crossing over take place at chiasma to exchange genetic materials between non-identical chromatids, in order to produce new combination of gene
• centrioles move towards opposite pole
• spindle fibre form
• nucleus membrane disintegrate
• nucleolus disappear

Metaphase 1:
- homologous chromosome arranged randomly in a single row at the equatorial plane

Anaphase 1:

• spindle fibre shorten and contract
• holomogous chromosome are separated
• chromosomes are attracted to the opposite poles

Telophase 1:

• chromosomes arrive opposite poles cell
• spindle fibre disappear
• nucleus membrane and nucleolus reformed
• two daughter cells are in haploid condition

Meiosis 2:

• produce four haploid daughter cells
• each haploid cell contain half the number of parent cell chromosome
• each cell develop into gamates

Question 9

2 types of tumour

Answer 9

1. Benign tumour
   - not dangerous
   - can be removed by surgery
2. Malignant tumour
   - cancer
   - caused by radiation, bacteria, virus, chemical substances, carcinogen
   - cell divide continuously and develop into tumour
   - cancer cell spread and destroy the normal cells around them
   - affect the function of tissue around them
   - if not identified at the early stage, could damage the organs and finally death

Question 10

how does tumour spread

Answer 10

• tumour grows from a single cell
• cancer cells compete with other cell to get nutrient
• spread through the lymph vessel and blood vessel to other parts of body
• new tumour develop on other organs