1. Review How many chromosomes do you have in each cell?
How many sets of your chromosomes do you have (1, 2, 3, 4, more?)
How many of each type of chromosome is inherited from your mom?
How many of each type of chromosome is inherited from your dad?
How many sex chromosomes do you have.

2. Meiosis Remember: Mitosis “happens in my toesies”
Meiosis happens in my ovaries

3. If parents have two copies of each chromosome, why and how do they pass on only one to their offspring?
MEIOSIS is the process of cell division that decreases the number of chromosomes to make sperm or egg cells
Original cell
Sperm or egg cells

4. The purposes of Meiosis:
Reduce the total number of chromosomes by half so that only ONE chromosome from each pair is inherited from each parent.
Produce variation in offspring by:
randomly “sorting” (pairing up) the homologous chromosomes when the gametes meet.
exchanging (crossing over) homologous chromosome arms

5. Meiosis Diploid: pairs of homologous chromosomes
Original cell
Diploid: pairs of homologous chromosomes
Crossing over occurs here
Sperm or egg cells
Haploid single chromosomes

6. Fertilization Gametes: Zygote: (haploid sex cells) (diploid embryo)
Sperm
Egg
Gametes:
(haploid sex cells)
Zygote:
(diploid embryo)
Fertilized egg

7. Meiosis Overview
Each pair of chromosomes first replicates to form sister chromatids.
The cell then divides twice without any further replication of DNA.
The first division separates the homologues (Meiosis 1).
The second division separates the 2 sister chromatids (Meiosis 2).

8. Comparison of meiosis and mitosis
Draw and label each step on your worksheet.
Fill in the concept map.
Meiosis animation
Mitosis animation