Meiosis

Question 1

What is a gamete?

Answer 1

haploid sex cell. Sperm = male (small) egg=female (big)

Question 2

What does haploid (n) mean?

Answer 2

a cell with a single set of unpaired chromosomes (one of each homologous pair)

Question 3

What does diploid (2n) mean?

Answer 3

A cell with two complete sets of chromosomes (both homologous pairs- one from each parent)

Question 4

What does homologous pairs mean?

Answer 4

One chromosome from each parent. Same genes but different alleles

Question 5

What happens in fertilisation? How does it increase genetic variation within species?

Answer 5

A haploid sperm fuses with a haploid egg, making a cell with the normal diploid number of chromosomes. Random fertilisation produces zygotes with different combinations of chromosomes to both parents. Mixing of genetic material increases genetic diversity within a species

Question 6

What is meiosis?

Answer 6

Cell division that produces gametes. Involves two nuclear divisions resulting usually in the formation of four haploid daughter cells (genetically different from each other) from a single diploid parent cell. +crossing over and independent segregation

Question 7

before meiosis (early and late interphase)

Answer 7

DNA unravels and replicates so there are two copies of each chromosome called chromatids
Early interphase (2n) - 6 chromosomes, 3 homologous pairs
Late interphase (2x2n) - 6 chromosomes, 3 homologous pairs

Question 8

What happens in prophase 1

Answer 8

(2x2n) chromosomes condense and become visible, nuclear membrane breaks down

Question 9

What happens in metaphase I?

Answer 9

(2x2n) homologous pairs line up at the equator, spindle fibres form attach to the centromeres

Question 10

What happens in anaphase I?

Answer 10

(2x2n) homologous pairs separate and are pulled apart to opposite poles

Question 11

What happens in telophase I?

Answer 11

Nuclei reform and cell divides (2xn and 2xn)

Question 12

What happens in prophase II?

Answer 12

Nuclei break down (2xn and 2xn)

Question 13

What happens in metaphase II?

Answer 13

Chromosomes line up at the equator. Spindle forms attaches to centromeres (2xn and 2xn)

Question 14

What happens in Anaphase II?

Answer 14

sister chromatids separate and pulled apart to opposite poles (2xn and 2xn)

Question 15

What happens in Telophase II?

Answer 15

(n, n , n , n) Nuclei reform. Cell divides. Four haploid cells genetically different to each other are produced.

Question 16

What is crossing over of chromatids.

Answer 16

During metaphase of meiosis I, chromatids of homologous pairs cross over and swap alleles. Chromatids still contain same genes but now have a different combination of alleles

Question 17

What is independent segregation of chromosomes?

Answer 17

When homologous pairs are separated it’s completely random which chromosome from each pair ends up in which daughter cell. So the four daughter cells have different combinations of chromosomes leading to genetic variation.

Question 18

How to tell where meiosis happens in life cycle

Answer 18

Meiosis needed for sexual reproduction (produces gametes)

Question 19

outcome of meiosis

Answer 19

four genetically different daughter cells, with half the chromosome number as the parent cell

Question 20

Outcome of mitosis

Answer 20

two genetically identical daughter cells, with the same chromosome number as the original cell