Chromosomes

•Chromosomes are passed on - along with the genes on the chromosomes - from parents to offspring.•If each parent contributed all chromosomes to an offspring, then the offspring would have twice as many chromosomes as the parents - twice the normal number of chromosomes.•This does not happen because of a process called MEIOSIS.

•Chromosomes contain genes whose main function is to produce proteins. These proteins determine traits of an organism.

Chromosome

- determines traits

(ie. hair color, shape of nose)

Gene

Meiosis

•Meiosis is sexual reproduction.

•Your body is made up of trillions of cells.

•Most of those - including bone, muscle and skin cells - have 46 chromosomes in each nucleus.

•Sex cells have 23 chromosomes each nucleus.

•Meiosis is a type of cell division that produces sex cells (sperm or egg) with half as many chromosomes as body cells.

1. The parent cell gets ready to divide. It contains 46 chromosomes.

2. Each chromosome doubles.

3. The chromosomes pair up by size and l ine up across the center of the cell.

4. The chromosomes separate. The split p airs move to the opposite side of the cell. The cell divides.

5. Two new cells ar e formed. Each contains half of the pairs from step 2.

6. The chromosomes again line up across the center of each new cell.

7. The resulting chromosomes separate, half move to the opposite side of

each cell. Each cell divides.

8. Four cells are formed. Each cell contains 23 single chromosomes.

8. Four cells are formed. Each cell contains 23 single chromosomes.

Final product - 4 sex cells

4 eggs or 4 sperm

Each has half the chromosomes as the

parent cell.