1. Section 6-6 “Genetic Variation”

2. On notebook paper
Title : Notes 6.6 Genetic Variation
3 Main Ways
During Meiosis (why ?)
Fertilization: (why?)
Crossing Over
Draw Picture Page 190

3. KEY CONCEPT Independent assortment and crossing over during meiosis result in genetic diversity

4. Sexual reproduction creates a unique combination of genes
independent assortment of chromosomes in meiosis
random fertilization of gametes

5. Crossing over during meiosis increases genetic diversity
Crossing over is the exchange of chromosome segments (pieces) between homologous chromosomes
this results in new combinations of genes
occurs during prophase I of meiosis I

7. Homologous Chromosomes
Crossing Over:
Before Cross over
After Cross over
Homologous Chromosomes

8. In mitosis, offspring are identical to the “parent” cell
Genetic Variation
In mitosis, offspring are identical to the “parent” cell
In meiosis, chromosomes and the genetic information they carry are shuffled resulting in genetic variation

9. Chromosomes contain many genes
The farther apart two genes are located on a chromosome, the more likely they are to be separated by crossing over
Genes located close together on a chromosome tend to be inherited together, which is called genetic linkage

10. Mutations: Spontaneous changes in DNA
These can result in good changes or bad changes in the traits
We’ll learn more about mutations when we talk about DNA.

11. Human body cells have 46 chromosomes, and sex cells have 23
Are You Unique?
Human body cells have 46 chromosomes, and sex cells have 23
The number of different kinds of sperm or eggs that can be produced is 223
When an egg and sperm unite you get 223 x That’s over 70 trillion different zygotes that could be formed during sexual reproduction in humans