Slide 1 of 27

Meiosis: An Overview

Assume that an organism has:1 Homologous Pair = 2 Chromosomes(Diploid cell – 2n)

STEP 1: Each of the chromosomes is replicated in Interphase

STEP 2: Chromosome pairs of copies separate in Meiosis I(Haploid cell – n)BUT 2 copies of each one

STEP 3: Each of the copies (sister chromatids) in a cell separates creating 4 haploid cells(Haploid cell with only 1 copy)

Slide 2 of 27

Repeat the Diagram but with 4 Chromosomes

The cell before interphase has 4 chromosomes and is diploid

Indicate how many chromosomes are present:

1. After interphase but before Meiosis

2. After Meiosis I

3. After Meiosis II

Slide 3 of 27

Repeat the Diagram but with 4 Chromosomes ANSWERS The cell before interphase has 4 chromosomes and is diploid

Indicate how many chromosomes are present:

1. After interphase but before Meiosis – Equal to 8 chromatids

2. After Meiosis I

-- 4 chromosomes

-- 2 Cells of 2 chromsomes (4 chromatids each cell) (haploid)

3. After Meiosis II

-- 8 chromosomes

-- 4 cells of 2 chromosomes (2 chromatids per cell) (haploid)

Slide 4 of 27

Questions?

If a cell has 10 chromosomes and is diploid, how many chromosomes (include what the book calls chromatids) are found at:

A) the end of Meoisis I

B) the end of Meiosis II

Slide 5 of 27

Questions? ANSWERS

If a cell has 10 chromosomes and is diploid, how many chromosomes (include what the book calls chromatids) are found at:

A) the end of Meoisis I

-- 10 chromosomes (2 cells of 5 chromosomes)

-- 20 chromatids (2 cells of 10 chromatids)

B) the end of Meiosis II

-- 20 chromosomes (4 cells of 5 chromosomes)