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Published byHillary Leslie King Modified over 9 years ago
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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
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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
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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
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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
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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
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Genetic Linkage
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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.
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