Meiosis

Question 1

what are the 2 types of cell division?

Answer 1

mitosis and meiosis

Question 2

what is mitosis

Answer 2

the division of somatic (body) cells. It produces
2 diploid cells (2n)

Question 3

what is meiosis

Answer 3

the division of cells to produce gametes. It produces 4 haploid cells (n)

Question 4

diploid vs haploid

Answer 4

Diploid cells have the full set of chromosomes (46 in humans) whereas haploid cells have a half set.

Question 5

what are gametes, where are they produced?

Answer 5

Gametes are sex cells and they are produced in gonads.

Question 6

gametes in plants vs animals

Answer 6

In animals: eggs and sperm, produced in ovaries & testes
In plants: the gametes are ovules and pollen

Question 7

what is a homologous pair

Answer 7

Diploid cells have 2 chromosomes that contain the same genes. One was inherited from each parent. Such chromosomes are called homologous pairs.

Question 8

how many homologous pairs do humans have?

Answer 8

Humans = 46 chromosomes = 23 pairs
22 homologous pairs of autosomes (non-sex chromosomes) and 1 pair of sex chromosomes.

Question 9

what must happen before cell division and how does this occur?

Answer 9

Before cells divide, the chromosomes must replicate, or make another copy of themselves. They do this using the base-pairing rules. A & T, G & C

Question 10

what happens when the chromosome replicates, what is each strand called and how are they held together?

Answer 10

The chromosome becomes double-stranded.
Each strand is called a chromatid and the chromatids are held together by a centromere.

Question 11

what are the 5 stages of cell division and what occurs before?

Answer 11

Interphase

Prophase

Metaphase

Anaphase

Telophase

Question 12

interphase

Answer 12

the chromosomes replicate
but are NOT visible

Question 13

prophase 1

Answer 13

• chromosomes “wind up”
• nuclear membrane breaks
  down
• centrioles move to the poles

Question 14

metaphase 1

Answer 14

• spindle fibres form
• chromosomes attach to
  spindle fibres at the equator (middle)
  in their homologous pairs (2 copies
  of the same chromosome - one from each parent

Question 15

anaphase 1

Answer 15

chromosomes move
to either end of the cell

Question 16

telophase 1

Answer 16

• the original cell divides into 2
  by the cell membrane pinching in
  (cytokinesis)
• the nuclear membrane may
  reform

Question 17

prophase 2

Answer 17

• if the nuclear membrane reformed, it again breaks down

Question 18

metaphase 2

Answer 18

• chromosomes attach to the spindle fibres at the middle of the cell
  (not in homologous pairs this time)

Question 19

anaphase 2

Answer 19

• the chromosomes split and one
  chromatid moves to each end of
  the cell.

Question 20

telophase 2

Answer 20

• each cell divides into 2 by cytokinesis
• the nuclear membranes reform
• the chromosomes “unwind”
• this all means that the original cell has produced 4 haploid daughter cells.

Question 21

overview of the 8 steps in Meiosis

Answer 21

1. Before meiosis starts, the parent cell replicates its DNA.
2. The chromosomes then move to the centre of the cell.
3. Homologous chromosomes are separated. This is an important step that does not happen in mitosis
4. The cell membrane pinches the cell in half. Both daughter cells then enter a second round of division.
5. Again, chromosomes move to the centre of the cells.
6. This time sister chromatids are separated.
7. The cell membrane pinches both cells in half.

Question 22

how does meiosis relate to inheritance

Answer 22

Genetic variation is increased by meiosis. During fertilisation, 1 gamete from each parent combines to form a zygote. Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA.

Question 23

IPMAT

Answer 23

Party
middle
apart
two