1. The Cell and Inheritance
In 1903, an American geneticist, named Walter Sutton studied the cells of grasshoppers.
Focused on the movement of chromosomes during the formation of sex cells
Discovered that grasshopper’s sex cells have half the number of chromosomes as their regular body cells.
One chromosome in each pair came from each parent.

2. Genes are carried from parent to their offspring on chromosomes.
Idea
Sutton’s idea came to be
known as the Chromosome Theory of
Inheritance.
Genes are carried from parent to their offspring on chromosomes.

3. Meiosis
How do sex cells end up with half the number of chromosomes as body cells?
Meiosis
Chromosome pairs separate
They are distributed into 2 different cells
The resulting sex cells only have half as many chromosomes.

4. Meiosis Before meiosis- every chromosome in the parent cell is copied
Meiosis I-
chromosome pairs line up in the center
The pairs separate and move to opposite ends
2 cells form, each with half the number of chromosomes, each chromosome still has 2 chromatids

5. Meiosis cont. Meiosis II-
The chromosome with their 2 chromatids move to the center of the cell
Centromeres split and chromatids separate, single chromosome move to opposite ends of the cell
End of meiosis- 4 sex cells have been produced, each with only half the number of chromosome as the parent cell in the beginning

8. Line up of Genes
The human body contains 23 chromosome pairs for a total of 46 chromosomes.
Chromosomes are made up
of many genes, like beads on
a string.
Those 23 pairs of chromosomes
contains 20,000 to 25,000 genes
Each gene controls a trait.

9. Traits are passed from one generation to the next
Genetic Principles
Traits are passed from one generation to the next
Traits are controlled by genes
Genes are inherited in pairs, 1 gene from each parent

10. 4. Genes can be dominant or recessive
5. Dominant genes “hide” recessive genes
6. Some genes are neither dominant nor recessive; they show incomplete dominance