Chapter 8: 8.4 Meiosis

Question 1

Meiosis

Answer 1

Process of cell division
* Specifically produce gametes

Question 2

Gametes

Answer 2

Sex cells
* Sperm and Eggs

Question 3

Mitosis vs. Meiosis

• Chromosome count
• Number of cells

Answer 3

Mitosis
* 2 daughter cells
* Each cell has identical number of chromosomes as original cell

Meiosis
* 4 daughter cells
* Each cell has half the number of chromosomes as original cell

Question 4

Why do sperm and egg cells have half the number of chromosomes?

Answer 4

When they fuse, they produce a diploid fertilized egg

Question 5

Does meiosis produce haploid or diploid cells?

Answer 5

Haploid

Question 6

Is meiosis a two step process or a multi step process?

Answer 6

Two steps
* Meiosis I
* Meiosis II

Question 7

What stages does a cell undergo in meiosis?

Answer 7

In EACH round of cell division:
* Interphase
* Prophase
* Prometaphase
* Metaphase
* Anaphase
* Telophase

Question 8

When does interphase occur in meiosis?

Answer 8

Before entering meiosis I

Question 9

What phases are included in interphase before meiosis I?

Answer 9

• G1 phase
• S phase
• G2 phase

Question 10

What happens in each stage of interphase before meiosis I?

Answer 10

1. G1 phase: Cell grows
2. S phase: DNA is replicated
3. G2 phase: Cell prepares for division

Question 11

Meiosis I:

Prophase

Known as Prophase I in Meiosis I

Answer 11

• Chromosomes begin to condense
• Each crhosome lines up with homologous pair
• Overlap forms
• Crossing over occurs

Question 12

Meiosis I:

Prophase I terminology:
1. Chromosomes lining up with its homologous pair
2. The overlap formed by the pair of chromosomes

Answer 12

1. Synapsis
2. Chiasmata

Question 13

Meiosis I:

What is crossing over in Prophase I?

Answer 13

The exchange of DNA between the two homolgous chromosomes

Question 14

Meiosis I:

Metaphase I

Known as Metaphase I in Meiosis I

Answer 14

• Chromosomes move to metaphase plate (after crossing over)
• Homologous pairs line up in a random orientation

Question 15

Meiosis I:

Compared to mitosis, what is different in Metaphase I?

Answer 15

Homologous pairs line up
* Instead of individual chromosomes

Question 16

Meiosis I:

In Metaphase I, why do the homologous pairs line up in random orientation?

Answer 16

Independent assortment

Question 17

Meiosis I:

Anaphase I

Known as Anaphase I in Meiosis I

Answer 17

• Homologous chromosomes are pulled apart by the microtubules

Question 18

Meiosis I:

Compared to mitosis, what is different in Anaphase I?

Answer 18

Sister chromatids remain attached
* They are separated in mitosis

Question 19

Meiosis I:

Telophase I

Known as Telophase I in Meiosis I

Answer 19

• Chromosomes are separated
• Cytokinesis occurs

Question 20

What is the end product of Meiosis I? What is the end stage of Meiosis I?

Answer 20

Telophase I + Cytokinesis
* Result: Two haploid daughter cells

Question 21

Chromosomal Cross-over
* When does it occur?

Answer 21

Prophase of Meiosis I

Question 22

What does chromosomal cross-over result in?

Answer 22

Genetic variation (i.e. new genotypes)

Question 23

Explain:

Mechanism of chromosomal cross-over

Answer 23

Chromosomes swap portions which contain various genes (or alleles which are versions of a gene)

Question 24

Can cross-over exist a multiple locations?

Answer 24

Yes it can, BUT the locations must be homologous to each other
* Contain the same corresponding alleles

Question 25

What stages occur in Meiosis II?

Answer 25

• Prophase II
• Metaphase II
• Anaphase II
• Telophase II
• Cytokinesis

All phases are known as “II” in Meiosis II

Question 26

What is the result of Meiosis II?

Answer 26

4 haploid daughter cells