1. Learning Target: Meiosis & Genetic Variation Learning Target: Meiosis & Genetic Variation I Can…Explain how crossing over during meiosis contributes to genetic diversity. I Will… Describe what occurs to homologous pairs of sister chromatids during crossing over Define gene linkage Explain why some genetic traits are always inherited together

2. Meiosis and Genetic Variability Ch. 6.6 (pp. 189 – 191) Meiosis and Genetic Variability Ch. 6.6 (pp. 189 – 191) KEY CONCEPT: Independent assortment and crossing over during meiosis result in genetic diversity. Main Idea: Sexual reproduction and random pairing of gametes creates unique gene combinations You are not just one-in-a-million, You are one-in-over 70 trillion

3. One human germ cell starting with 23 pairs of chromosomes results in over 8 million possible genetic combinations of haploid gamete cells (eggs and sperm) Now, sperm meets egg… A sperm with a 2 23 or 8 million possible genetic variation combination from the father’s germ cell An egg with a 2 23 or 8 million possible genetic variation combination from the mother’s germ cell Result: Offspring with 1 of the over 70 trillion possible genetic variation combinations meets

4. Crossing over during meiosis increases genetic diversity. Crossing over: Exchange of chromosome segments between homologous sister chromatid pairs Results in new combinations of genes on the DNA Chromosome thread

5. Genetic Linkage Two genes located far apart on a chromosome are more likely to be separated by crossing over Genes located close together on a chromosome tend to be inherited together

6. Genetic Linkage

7. Learning Check: Meiosis & Genetic Variation Learning Check: Meiosis & Genetic Variation Are you really just a genetic combination of your mother and father? Explain why you feel you are or are not.