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How are genes inherited?

How are genes inherited? . The parents. Homer has straight hair. Marge has curly hair. The families . Is hair curliness controlled by genes or by the environment?. Homer. Homer has straight hair Every cell in Homer has two sets of genes Homer’s has two straight hair genes

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How are genes inherited?

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  1. How are genes inherited?

  2. The parents Homer has straight hair Marge has curly hair

  3. The families Is hair curliness controlled by genes or by the environment?

  4. Homer • Homer has straight hair • Every cell in Homer has two sets of genes • Homer’s has two straight hair genes • We can show the straight hair gene with a capital S • Homer’s genes: SS

  5. Marge • Marge has curly hair • Every cell in Marge has two sets of genes • Marge has two curly hair genes • We can show the curly hair gene with a small s • Marge’s genes: ss

  6. Making a new Simpson • Homer makes sperm • Each sperm has one gene for hair type • Homer only has straight hair genes • So all of his sperm have straight hair genes • Homer’s Sperm S S

  7. Making a new Simpson • Marge makes eggs • Each egg has one gene for hair type • Marge only has curly hair genes • So all of her eggs have curly hair genes • Marge’s Eggs s s

  8. Making a new Simpson S s S s S s S S S s s s

  9. Making a new Simpson • All of the Simpson babies have one gene for curly hair and one gene for straight hair • So what type of hair do they have? Ss Ss Ss Ss

  10. Making a new Simpson • THEY ALL HAVE STRAIGHT HAIR! • The straight hair gene is DOMINANT • Just one copy of this gene will give you that characteristic • The curly hair gene is RECESSIVE • You need two copies of the gene to have that characteristic Ss

  11. Liking donuts • Homer likes donuts • Every cell in his body has two donut genes. • His genes are: D D • Homer’s sperm D D

  12. Liking donuts • Marge doesn’t like donuts. • Every cell in her body has two no donut genes • Her genes are: d d • Marge’s Eggs d d

  13. Making a new Simpson D d D d D d D D D d d d

  14. Making a new Simpson • Liking donuts is dominant • Do the Simpson children like donuts? Dd Dd Dd Dd

  15. Weight • Marge has normal weight. • Both of her weight gens are for normal genes • Her genes are: N N • Marge’s Eggs N N

  16. Weight • Homer does not have normal weight. He is obese. • Both of his weight genes are for obesity (not normal weight) • His genes are: n n • Homer’s sperm n n

  17. Making a new Simpson • Normal weight is dominant • What weight do all the Simpson children have? Nn Nn Nn Nn

  18. Practice

  19. The next generation? • Lisa has straight hair • Every cell in Lisa has two sets of genes • Lisa has one gene for straight hair, which is dominant. • She also has one gene for curly hair, which is recessive. • Lisa’s genes: Ss

  20. The next generation? • Milhouse has straight hair • Every cell in Milhouse has two sets of genes • Milhouse has one gene for straight hair, which is dominant. • He also has one gene for curly hair, which is recessive. • Milhouse’s genes: Ss

  21. The next generation? • Milhouse’s genes: Ss • Lisa’s genes: Ss S s S s

  22. The next generation? S S S s s S s S s s S s

  23. The next generation • Straight hair is dominant • How many children have straight hair? • How many have curly hair? SS ss Ss Ss

  24. The next generation

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