Cell Division

Question 1

what are the two types of cell division?

Answer 1

mitosis and meiosis

Question 2

what must happen before a cell divides?

Answer 2

the chromosomes replicate making an exact copy of themselves - this doubles the amount of DNA in the cell

Question 3

what does mitosis do?

Answer 3

• produces genetically identical daughter cells
• cells are diploid - they have one pair of each chromosome in each nucleus
• used for growth, repair and asexual reproduction

Question 4

what is a human diploid cell?

Answer 4

a cell that has 23 pairs of chromosomes (46 in total)

Question 5

what does meiosis do?

Answer 5

• produces haploid gametes (sperm, egg, pollen) which are not genetically identical
• meiosis is only used to produce gametes for sexual reproduction

Question 6

what is a human haploid cell?

Answer 6

haploid cells have 23 chromosomes in total (unpaired)

Question 7

what is a consequence of meiosis?

Answer 7

is that every gamete is produced is genetically different - it carries different alleles to every other gamete

Question 8

what is variation in offspring produced by?

Answer 8

• genetic variation in gamete cells produced by meiosis
• random fertilisation of ova (egg cells) by male gametes

Question 9

differences between mitosis and meiosis processes?

Answer 9

mitosis:
- produces genetically identical daughter cells
- produces two cells
- involves one division
- produces diploid cells in humans
- keeps the same chromosome number

meiosis:
- produces genetically non-identical daughter cells
- produces four cells
- involves two cell divisions
- produces haploid cells in humans
- halves the number of chromosomes

Question 10

differences between role of mitosis and meiosis?

Answer 10

mitosis:
- generates all adult cells except gametes (growth and repair)
- occurs throughout the human body
- occurs throughout a plant
- used for asexual reproduction (cloning)

meiosis:
- only used to produce gametes
- only occurs in ovary and testis (human)
- only occurs in ovary and anther (plant)
- used for sexual reproduction

Question 11

what is mitosis?

Answer 11

mitosis is a type of cell division in which a diploid body cell copies itself and finally divides into two identical diploid daughter cells. the daughter cells are clones of each other. every base pair of their DNA is identical.

Question 12

process of mitosis

Answer 12

1. the cell grows.
2. the DNA replicates (is copied) to form two copies of each chromosome. these copies
   (chromatids) are joined together at a single point (the centromere).
3. the nuclear membrane breaks down. The chromosomes line up across the centre of the cell, attached to special spindle fibres
4. the chromatids (copies of chromosomes) are pulled apart and move to opposite ends of the cell.
5. the cytoplasm and cell membrane divides to form two identical cells.

Question 13

what is meiosis?

Answer 13

the type of cell division which gives rise to cells that are genetically different

Question 14

where does meiosis take place?

Answer 14

in the sex organs

Question 15

where are meiosis cells formed?

Answer 15

in the gametes

Question 16

why are gametes different from other cells?

Answer 16

half the normal number of chromosomes (they are haploid)

Question 17

meiosis process

Answer 17

1. the parent cell grows.
2. the DNA replicates (is copied) to form two copies of each chromosome. these copies
   (chromatids) are joined together at a single point (the centromere).
3. the nuclear membrane breaks down. the homologous pairs of chromosomes join together.
4. the homologous pairs of chromosomes exchange sections of DNA. they then attach to the spindle fibres in pairs, at the centre of the cell.
5. the homologous pairs of chromosomes are pulled apart and move to opposite ends of the cell. the cell divides.
6. the chromosomes line up along the centre of the cell, attached to the spindle fibres. the
   chromatids separate and move to opposite ends of the cell. Each cell divides again.