1. Warm Up: “Should This Dog Be Called Spot?”
Imagine this microscopic drama:
A sex cell from a male dog joins with a sex cell from a female dog. Each dog’s sex cell carries 39 chromosomes. The fertilized egg (zygote) that results contains 78 chromosomes. It receives a set of chromosomes from each parent. Suppose that you could look at one pair of the fertilized egg’s chromosomes…
Worksheet

2. Ch. 5, Sect. 3: Meiosis
Where are genes located (on chromosomes), and how do they pass information?
Understanding reproduction is the first step in finding the answers!

3. Foldable
Asexual Reproduction
Sexual Reproduction
Mitosis
Meiosis

4. Two Types of Reproduction
Asexual Reproduction
Only one parent cell is needed
A parent
Offspring are identical to parent cell
Structures inside the cell are copied, then the parent cell divides
Remember mitosis?
Mitosis – process of producing cells identical to the parent cell (including the number of chromosomes)
Why?
Unicellular organisms – reproduction
Multicellular organisms – growth & repair

5. Mitosis

6. Mitosis
Copy this illustration (including labels) to the front of your foldable.

7. Two Types of Reproduction
Sexual Reproduction
Two parents cells join together
Offspring are different from both parents
Parent cells = sex cells (gametes)
Sperm or eggs
Join together at fertilization
Sex cells have half the number of chromosomes as the organism so that they have a full set after fertilization. 23 23 46

8. Chromosomes
Human body cells have 46 chromosomes (or 23 homologous pairs of chromosomes).
Homologous chromosomes – chromosomes that carry the same sets of genes (but possibly different alleles)

9. Homologous Pair of Chromosomes
Chromosomes that have the same sequence of genes and the same structure
Analogy: Pair of shoes
Sex cells (egg or sperm) have only half of the homologous pair (only 23 single chromosomes).
Analogy: One shoe

10. Meiosis Sex cells are made during the process of meiosis.
Meiosis – process that produces sex cells (egg or sperm) with half the usual number of chromosomes
Sex cells have half of the homologous pair
Two cell division (vs. one in mitosis)

11. Meiosis

12. Meiosis

14. Comparison of the Two Processes
MITOSIS
MEIOSIS