Mini Lesson#4 Meiosis

MEIOSIS- Sexual Reproduction

gamete/sex cells(eggs and sperm) are

Produced through Meiosis.

Meiosis Only Takes Place at— Male

–Testes

– Sperm cell Formation

Number of Chromosomes

-23(Half)

Female

- Ovaries

– Egg cell Formation

Number of Chromosomes

-23 (Half)

Each cell is unique and different !!!

Meiosis divides twice!!

Gametes have half the # of chromosomes

compare to body cells

Meiosis

sexual reproduction

Two divisions (meiosis I and meiosis II).

Meiosis I Four phases:

a. prophase I

b. metaphase I

c. anaphase I

d. telophase I

Meiosis 2 Four phases:

a. prophase ll

b. metaphase Il

c. anaphase Il

d. telophase Il

Crossing Over (During Prophase I)

Create Genetic Variations!!

Prophase I

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__unique_features_of_meiosis.html Crossing Over

Meiosis I & Meiosis II

How is Meiosis different from Mitosis?

Mitosis Meiosis Type of reproduction

Number of divisions

Number of daughter cells

Kind of cells

Chromosome number

Similarity of offspring

Crossing over?

Visual

How is Meiosis different from Mitosis?

Mitosis Meiosis Type of reproduction

Asexual Reproduction Sexual Reproduction

Number of divisions 1 division 2 divisions

Number of daughter cells 2 daughter cells 4 daughter cells

Kind of cells

ALL Cells except sex cells Gametes, Sex Cells ( egg cells and sperm cells) ONLY

Chromosome number Same (ex: Parent-46 Daughter- 46)

Half (ex: Parent-46 Daughter- 23)

Similarity of offspring Identical Different from parents - Variation

Crossing over?

No Yes. Exchanging partial chromosomes

Visual