MEIOSIS

1
MEIOSIS
Creating gametes (sex cells)
2
Mitosis vs Meiosis

1. Purpose growth and repair
2. Occurs in somatic cells
3. Results in two identical cells
4. Both cells are diploid 2N
5. Example

3
1. Chromosome Number

1. A human body cell has 46 chromosomes
2. 23 from dad and 23 from mom
3. These sets of chromosomes are homologous, meaning
   that each chromosome that came from dad has a
   corresponding chromosome from mom.

4
2. Diploid and Haploid

1. A cell that contains both sets of homologous
   chromosomes is said to be diploid.
2. Diploid two sets, 2N, or 2N46
3. A cell that only contains 1 set of chromosomes is
   said to be haploid.
4. Haploid one set, N, or N23

5
3. Phases of Meiosis

1. Occurs in 2 divisions- meiosis I and meiosis II
2. In the end one diploid cell will become 4 haploid
   cells

6
4. Crossing Over occurs in Meiosis I

1. Homologous chromosomes form a tetrad
2. Chromatids cross over one another
3. The crossed sections of chromatids are exchanged
4. This produces a new combination of genes which
   contributes to diversity within a population.

7
5. Gamete Formation occurs in Meiosis II

1. Meiosis I results in 2 haploid daughter cells
2. Meiosis II results in 4 haploid daughter cells
3. The haploid gamete in males is sperm
4. The haploid gamete in females is the egg

8
Males vs. Females

9
6. Comparing Mitosis and Meiosis

• a. Mitosis
• Results in 2 identical
• diploid
• Involves asexual reproduction
• Somatic cells
• 1 division

• b. Meiosis
• Results in 4 genetically different cells
• haploid cells
• Involves sexual reproduction
• gametes
• 2 divisions

10
(No Transcript)
11

• Genetic variation through
• Crossing Over at prophase I
• Independent Assortment at metaphase I
• Random Fertilization (sperm to egg)

12
conclusion

• Meiosis is a linear process as opposed to the
  cell cycle
• Meiosis is how sexually reproducing organisms
  make gametes. In contrast mitosis allows an
  organism to make new cells for growth and repair
  asexually.