Unit 3: Meiosis

Question 1

What does ploidy mean ?

Answer 1

The number of sets of chromosomes in a cell

Question 2

What does haploid mean ?

Answer 2

One set of chromosomes in a cell

Question 3

What does diploid mean ?

Answer 3

Two sets of chromosomes in a cell

Question 4

What is the haploid number (n) ?

Answer 4

The number of chromosomes in a gamete (a haploid sperm or egg cell)

Question 5

If haploid cells are n what does that make diploid and tetraploid cells ?

Answer 5

Diploid = 2n
Tetraploid = 4n

Question 6

What is a germ cell ?

Answer 6

Cells that will give rise ultimately to mature sperm and eggs

Question 7

What are somatic cells ?

Answer 7

Cells of the body that do not transmit information to the next generation

Question 8

What type of cells does meiosis occur in ?

Answer 8

Germ cells

Question 9

What are the 4 stages of Meiosis 1 ?

Answer 9

1) Prophase 1
2) Metaphase 1
3) Anaphase 1
4) Telophase 1 and cytokinesis

Question 10

What happens in prophase 1 ?

Answer 10

• Chromsomes condense
• Nuclear envelope breaks down
• Crossing over occurs

Question 11

What happens in metaphase 1 ?

Answer 11

• Pairs of homologous chromosomes move to the equator of the cell

Question 12

What happens in anaphase 1 ?

Answer 12

• Homologous chromosomes move to opposite poles of the cell

Question 13

What happens in telophase 1 and cytokinesis ?

Answer 13

• Chromsomes gather at poles of the cell
• Cytoplasm divides

Question 14

What are the 4 stages of meiosis 2 ?

Answer 14

1) Prophase 2
2) Metaphase 2
3) Anaphase 2
4) Telophase 2 and cytokinesis

Question 15

What are the 5 phases of prophase 1 ?

Answer 15

1) Leptotene
2) Zygotene
3) Pachytene
4) Diplotene
5) Diakinesis

Question 16

What happens during leptotene ?

Answer 16

• Duplicated chromosomes start to condense
• Nuclear envelope breaks down

Question 17

What happens during zygotene ?

Answer 17

• Bivalent forms
• Synapsis begins (synaptonemal complex forms)

Question 18

What happens during pachytene ?

Answer 18

• Synapsis is complete
• Crossing over occurs

Question 19

What happens during diplotene ?

Answer 19

• Chiasma is viable
• Synaptonemal complex disappears

Question 20

What happens during diakinesis ?

Answer 20

• Nuclear envelope fragments
• Bivalent ready for metaphase

Question 21

What is homologous recombination ?

Answer 21

The exchange of identical DNA sequences between similar or identical DNA molecules

Question 22

What is a chiasma ?

Answer 22

The point where 2 homologous chromosomes or chromatids exchange genetic material

Question 23

What is synapsis ?

Answer 23

Where homologous chromosomes pair up closely along their lengths

Question 24

What is crossover ?

Answer 24

Where homologous chromosomes exchange pieces of genetic material

Question 25

Explain the process of meiotic recombination (3)

Answer 25

1) Before the first mitotic division homologous chromosomes pair up
2) Chiasma forms, chromosomes swap bits of their arms
3) New ‘recombinant’ chromosomes formed each with different combinations of alleles to the parental chromosomes

Question 26

What are the 2 products of meiosis 2 ?

Answer 26

• Parental
• Recombinants

Question 27

How can position of chromosomes affect recombination ?

Answer 27

Genes that are in close proximity on a chromosome are less likely to be broken up by recombination