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Section 6-6 “Genetic Variation ”

Section 6-6 “Genetic Variation ”. Write everything that is underlined. KEY CONCEPT Independent assortment and crossing over during meiosis result in genetic diversity. 1. Sexual reproduction creates a unique combination of genes independent assortment of chromosomes in meiosis

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Section 6-6 “Genetic Variation ”

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  1. Section 6-6“Genetic Variation” Write everything that isunderlined

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

  3. 1. Sexual reproduction creates a unique combination of genes • independent assortment of chromosomes in meiosis • random fertilization of gametes • Unique phenotypes may give a reproductive advantage to some organisms

  4. You hold the cards in your hand • Let’s pretend that the deck of cards you hold in your hands represent some of the allelles that the parents have to pass on to their offspring. • Divide the cards evenly- don’t look at them! • When Miss Walsh tells each person to flip their cards, flip over one card. Miss Walsh will ask each group what they got. • What do you notice about the variation? • How does this apply to “crossing over” and genetic variation?

  5. A. Crossing over during meiosis increases genetic diversity 1. 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

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

  7. 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

  8. 2. 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

  9. 3. 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 next unit

  10. 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 223 . That’s over 70 trillion different zygotes that could be formed during sexual reproduction in humans

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