Chapter 2

Question 1

Meiosis

Answer 1

Formation of gametes in which the number of chromosomes is reduced

Question 2

Fertilization

Answer 2

Two haploid gametes fuse and restore the number of chromosomes to its original diploid value

Question 3

What are the five stages of prophase I

Answer 3

• Leptotene
• Zygotene
• Pachytene
• Diplotene
• Diakinesis

Question 4

Leptotene

Answer 4

Chromosomes condense and become visible

Question 5

Zygotene

Answer 5

Chromosomes continue to condense, homologous chromosomes pair up and begin synapse – a close association

Homologous pairs come together to form a synapse

Question 6

Bivalent/Tetrad

Answer 6

Each homologous pair of chromosomes, 2 chromosomes and 4 sister chromatids

Question 7

Pachytene

Answer 7

Chromosomes become shorter and thicker, and a three-part synaptonemal complex develops between homologous chromosomes

A protein between the two chromosomes form

Question 8

Crossing Over

Answer 8

In which homologous chromosomes exchange genetic information

Intra - chromosomal recombination

Question 9

Chiasma

Answer 9

The location where two chromosomes cross over

Question 10

Diplotene

Answer 10

The centromeres of the two homologous chromosomes move apart

Question 11

Diakinesis

Answer 11

Chromosome condensation continues…the nuclear membrane breaks down

Question 12

Metaphase I

Answer 12

Homologous chromosomes align up on the metaphase plate

Question 13

Anaphase I

Answer 13

Homologous chromosomes move apart – the sister chromatids remain attached

Question 14

Telophase I

Answer 14

The chromosomes arrive at the spindle poles, and the cytoplasm divides – interkinesis

Question 15

Interkinesis

Answer 15

The nuclear membrane reforms around the chromosomes clustered at each pole, the spindle apparatus breaks apart, and the chromosomes relax

Question 16

Prophase II

Answer 16

The events of interkinesis are reversed

Question 17

Metaphase II

Answer 17

sister chromatids align on the metaphase plate

Question 18

Anaphase II

Answer 18

The sister chromatids separate

Question 19

Telophase II

Answer 19

The chromosomes arrive at the spindle poles, a nuclear membrane reforms around the chromosomes and the cytoplasm divides – cytokinesis
chromosome become no longer visible

Question 20

What causes genetic variation?

Answer 20

1. Crossing Over in Prophase I
2. Random separation of homologous chromosomes in Metaphase I

Question 21

What evidence from yeast relay about crossing over?

Answer 21

Crossing over starts from zygotene and ends until the end of Prophase I

Question 22

Intra-chromosomal Recombination

Answer 22

The creation of new combinations of alleles on a chromatid

Question 23

Cohesins

Answer 23

They control the segregation or the separation of homologous chromosomes during mitosis and meiosis

• protein rings

Question 24

What holds homologous chromosomes together?

Answer 24

Cohesins along the chromosome arm hold homologs together

Question 25

What holds sister chromatids together?

Answer 25

Cohesins along the centromere hold sister chromatids along

Question 26

Which protein protect centromere cohesins during Anaphase I?

Answer 26

Shugoshin – “guardian spirit” in Japanese…is degraded later on before Anaphase II