Unit 3 - Ch 10 - Meiosis

Question 1

Phases of Meiosis

Answer 1

Interphase
Prophase I
Metaphase I
Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II

Question 2

Meiosis consists of _____ cell divisions

Answer 2

Two

Question 3

Events in Prophase I

Answer 3

1. Chromatin coils
   - chromosomes appear
2. nuclear membrane/nucleolus disappears
3. Synapsis occurs (tetrads)
   - homologous pairs align on top of each other to form tetrads = four sister chromatids
   - unique to meiosis*
4. Crossing over may occur
   - homologs exchange gene segments
   - this step produces varienty - random
   - sister chromatids are no longer identical (reason why siblings are genetically different)
   - unique to meiosis*

Question 4

Events of Metaphase I

Answer 4

1. Tetrads align on equatorial plate - unique to meiosis

Question 5

Events of Anaphase I

Answer 5

1. Homologous pairs separate

- unique to meiosis*

Question 6

Events of Telophase I

Answer 6

1. Chromosomes uncoil
2. Nuclear membrane/nucleolus reform
3. Cytokinesis usually follows

First cell division - results in two haploid gametes

Question 7

Events of Prophase II

Answer 7

1. Chromatin coils

2. Nuclear membrane/nucleolus disappears

Question 8

Events of Metaphase II

Answer 8

1. Replicated chromosomes (Sister chromatids) align on equatorial plate

Question 9

Events of Anaphase II

Answer 9

1. Sister chromatids separate

Question 10

Events of Telophase II

Answer 10

1. Chromosomes uncoil
2. Nuclear membrane/nucleolus reform
3. Cytokinesis

Second Cell Division - results in four haploid gametes

Question 11

Main characteristics of Meiosis (2)

Answer 11

1. Reduction division

2. Scrambles genetics

Question 12

How does meiosis scramble genetics?

Answer 12

1. Independent Assortment
   - tetrads align randomly on the Metaphase I plate
   - Mendel’s Second Law of Genetics
   = Humans - 8,338,608 combinations - 2 to the 23rd power
2. Crossing Over
   - occurs during synapsis
   - Prophase I
   - occurs randomly

Question 13

Explain reduction division

Answer 13

• Reduces the chromosome number by half
• eliminates homologous pairs
  = humans: Mother or Father 2n=46&raquo_space;> egg or sperm n=23&raquo_space;> zygote 2n=46

Question 14

Typical Plant Life Cycle

Answer 14

Alternation of Generations occurs between:

1. Sporophyte
2. Gametophyte

Question 15

Sporophyte

Answer 15

• (2n)

- produces spores meiotically (n) - conspicuous

Question 16

Gametophyte

Answer 16

• (n)

- produces gametes mitotically (n) - inconspicuous

Question 17

Role of meiosis in the typical animal life cycle

Answer 17

produces n gametes from 2n adults

Oogenesis
And
Spermatogenesis

Question 18

Oogenesis

Answer 18

Egg formation in the ovaries of females

a. Unequal Cytokinesis
- occcurs during meiosis I and II
- produces one large egg cell with lots of cytoplasm
- sustains embryo until implantation
- organelles originate in the zygote

b. Polar Bodies
- contain nuclear material from mother
- n (haploid)
- degenerate

Question 19

Spermatogenesis

Answer 19

Formation of sperm cells in the testes of males

- all four potential gametes are formed from each sperm producing cell

Question 20

Typical Fungal Life Cycle

Answer 20

Meiosis

• produces n spores from the diploid phase
• majority of the life cycle is haploid (fungal hyphee)