Cell Division

Question 1

What is mitosis?

Answer 1

Type of cell division that produces 2 genetically identical diploid daughter cells

Question 2

What is meiosis?

Answer 2

Type of cell division that produces 4 genetically different hjaploid daughter cells.

Question 3

What is interphase?

Answer 3

Longest stage of cell cycle where DNA replication occurs, production of organelles, protein synthesis and other process

Question 4

What is the role of mitosis?

Answer 4

Growth, repair and replacement of tissues

Question 5

What is the role of meiosis?

Answer 5

Formation of gametes so that sexual reproduction can occur.

Question 6

What are the stages of mitosis?

Answer 6

(P)rophase
(M)etaphase
(A)naphase
(T)elophase

Question 7

What is cytokinesis?

Answer 7

Constriction of the centre of the parent cell from the outside inwards resulting in 2 new cells

Question 8

What is cytokinesis in plants?

Answer 8

Where a cell plate forms at the equator of the parent cell and a new cell wall is laid down.

Question 9

What are sister chromatids?

Answer 9

A pair of identical chromatids formed by DNA replication, joined via a centromere.

Question 10

Describe what happens during meiosis 1 (prophase)

Answer 10

DNA condenses forming chromosomes and visible chromatids. Centrioles divide, migrating to opposite sides of the cell with spindle fibres developing extending from pole to pole. Paternal and Maternal chromosomes associate as homologous pairs (bivalents) in a process called synapsis, twist around one another, joining at chaismata, breaking and rejoining with equivalent chromatid. Nuclear membrane disintergrates and nucelolus disappears leaving the pairs of chromatids free in cytoplasm.

Question 11

Describe what happens during meiosis 2 (prophase)

Answer 11

Centrioles seperate and form a spindle at right angles to the previous spindle so that there are two spindles for each nucleus produced at telophase 1. The chromosomes condense and the nuclear membrane disappears.

Question 12

Describe what happens during meiosis 2 (metaphase)

Answer 12

The chromosomes arrange at the equatoe attached to spindle fibres via their centromeres . The centromeres replicate as they are pulled apart.

Question 13

Describe what happens during meiosis 2 (anaphase)

Answer 13

Spindle fibres contrcat and the centromere split causing teh chromatids to be pulled apart to opposite poles of the cell.

Question 14

Describe what happens during meiosis 2 (telophase)

Answer 14

The chromatids lengethen and the spindle fibres disappears . The nuclear membrane reforms and cytokinesis takes place.

Question 15

Describe what happens during meiosis 1 (metaphase)

Answer 15

Spindle fully formed, homologous pairs arrange of equator and attach to spindle fibres at centromere.

Question 16

Describe what happens during meiosis 1 (anaphase)

Answer 16

Spindle fibres contract causing the bivalent pairs to seperate and be pulled to opposite poles of cell. Chromosomes remain intact.

Question 17

Describe what happens during meiosis 1 (telophase)

Answer 17

Spindle fibres disappear, nuclear membrane reforms with nucleolus visible around each group of haploid chromosomes and thus have halve the number of chromosmes. Cytokinesis occurs

Question 18

What may unrestricted mitosis lead to?

Answer 18

Formation of tumors ( Irregular mass of cells that prevent rhe normal function of organs). Thought to occur due to mutations in the genes controlling cell division

Question 19

How does meiosis produce genetic variation?

Answer 19

1. Crossing over of chiasmata in meiosis 1
2. Random assortment of maternal and paternal chromsomes during metphase 1.

All result in new combinations of alleles.

Question 20

Describe what happens during mitosis (prophase)

Answer 20

DNA condenses forming chromosomes and visible chromatids. Centrioles divide, migrating to opposite sides of the cell with spindle fibres developing extending from pole to pole. Nuclear membrane disintergrates and nucelolus disappears leaving the pairs of chromatids free in cytoplasm.

Question 21

Describe what happens during mitosis (metaphase)

Answer 21

The chromosomes arrange
themselves at the centre or equator of the spindle. The chromosomes become attached to the spindle fibres at the centromere. Contraction of the spindle fibres draws the individual chromatids apart.

Question 22

Describe what happens during mitosis (anaphase)

Answer 22

Centromeres divide and the spindle fibres contract causing the chromatids to seperate and form individual chromosomes that are then pulled to either side of the cell with the centromeres leading the way.

Question 23

Describe what happens during mitosis (telophase)

Answer 23

Chromsomes have reached the poles of the cell and begin to uncoil and lengthen. The spindle breaks down and the nuclear membrane reforms with the nucleolus visible.

Question 24

What is the formula for mitotic index?

Answer 24

No. of cells in any stage of mitosis/ Total number of cells X 100

Question 25

What are chromosomes?

Answer 25

Long sections of DNA, histone protein and small amounts of RNA.

Question 26

What are chromatids?

Answer 26

Identical threads of DNA joined by a centromere and that lay parallel to one another

Question 27

What are diploid cells

Answer 27

Cells that contain the same number of chromosomes as their parental cell.

Question 28

What are haploid cells

Answer 28

Cells that contain halve the number of chromosomes as their parental cell.