Meiosis

Question 1

When does meiosis occur?

Answer 1

in sex cells for sexual reproduction producing gametes

Question 2

What is gametogenesis?

Answer 2

formation of haploid gametes

Question 3

What is fertilisation?

Answer 3

fusion of gametes to form a diploid zygote

Question 4

How many stages of meiosis are there?

Answer 4

2

Question 5

How does meiosis result in genetic variation?

Answer 5

crossing over during late prophase 1
independent assortment of chromosomes during metaphase 1
random fertilisation of gametes produced by genetically different parents

Question 6

How does crossing over occur?

Answer 6

homologous chromosomes pair up to form bivalents
adjacent paternal and maternal chromatids cross over
thus when chromosomes separate during anaphase 1, chromatids carry a combination of paternal and maternal genes

Question 7

What are points of crossing over in prophase 1 called?

Answer 7

Chiasmata

Question 8

What does independent assortment during metaphase 1 result in?

Answer 8

Gametes having different combinations of paternal and maternal chromosomes

Question 9

Why does random fertilisation result in genetic variation?

Answer 9

gametes are produced by genetically different parents
all gametes have an equal probability of being involved in fertilisation

Question 10

What are the stages of meiosis?

Answer 10

Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Cytokinesis
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2

Question 11

How many daughter cells are made from one parent cell in meiosis?

Answer 11

4 gametes

Question 12

What happens to the DNA, what does this mean?

Answer 12

DNA replication happens once
2 divisions therefore results in haploid daughter cells

Question 13

What id the diploid number of chromosomes in humans?

Answer 13

46 (23 pairs)

Question 14

What is the haploid number of chromosomes in humans?

Answer 14

23

Question 15

What happens during prophase 1 in meiosis?

Answer 15

chromosomes condense and attach to the nuclear envelope
synapsis occurs (pair of chromosomes line up close together) a tetrad composed of 4 chromatids is formed.
genetic recombination via crossing over may occur
the centrioles migrate away from one another and both the nuclear envelope and nucleoli break down

Question 16

What stage does a cell enter in meiosis after prophase 1?

Answer 16

metaphase 1

Question 17

What happens during metaphase 1 of meiosis?

Answer 17

chromosomes from mother and father pair up (homologous pairs)
tetrads align at the metaphase plate (on the equator of the spindle)
independent assortment occurs due to random alignment and division

Question 18

What stage happens after metaphase 1 of meiosis?

Answer 18

anaphase 1

Question 19

What happens during anaphase 1?

Answer 19

chromosomes move to opposite cell poles (microtubules interact to pull chromosomes to opposite ends of poles
sister chromatids remain together after homologous chromosomes move to opposite poles (unlike mitosis)

Question 20

WHat stage happens after anaphase1 of meiosis?

Answer 20

Telophase 1

Question 21

What happens during telophase 1?

Answer 21

chromosomes uncoil and lengthen
spindle fibres break down
nuclear envelope reforms
nucleolus reappears

Question 22

What occurs after telophase 1 in meiosis?

Answer 22

cytokinesis

Question 23

What happens during cytokinesis?

Answer 23

the division of the cytoplasm

Question 24

What happens in meiosis 2 in prophase 2?

Answer 24

the centrioles separate and organise a new spindle at right angles to the old spindle

Question 25

What happens during metaphase 2 of meiosis?

Answer 25

chromosomes line up on the equator, each chromosome attached to a spindle fibre by its centromere Independent assortment occurs as chromatids of chromosomes can face either pole

Question 26

What happens during Anaphase 2 of meiosis?

Answer 26

the centromeres divide and the spindle fibres shorten, pulling the chromosomes to opposite poles

Question 27

What happens during Telophase 2 of meiosis?

Answer 27

at the poles, the chromatids lengthen and can no longer be distinguished in the microscope. The spindle disintegrates and the nuclear envelope and nucleoli reform

Question 28

What does cytokinesis after telophase 2 of meiosis form?

Answer 28

4 haploid daughter cells (all genetically different)

Question 29

What happens before meiosis 1 that does not happen before meiosis 2?

Answer 29

DNA replication, the DNA is copied and doubled before meiosis 1 crossing over of chromosomes

Question 30

What are the differences between metaphase 1 and 2?

Answer 30

metaphase 1 aligns homologous pairs either side of the equator indecently assorts homologous chromosomes metaphase 2 aligns chromosomes on equator independently assorts chromatids

Question 31

What are the differences between anaphase 1 and anaphase 2 of meiosis?

Answer 31

separation at anaphase 1 forms chromosomes 2 daughter cells separation at anaphase 2 forms chromatids 4 daughter cells (all daughter cells are haploid)