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Ch14 Mendel

Ch14 Mendel. Mendel. http:// www.dnaftb.org /1/ animation.html. P generation – true-breeding. Why pea plants? distinct heritable features, or characters (such as flower color); character variants (such as purple or white flowers) are called traits He could control mating between plants

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Ch14 Mendel

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  1. Ch14 Mendel

  2. Mendel http://www.dnaftb.org/1/animation.html

  3. P generation – true-breeding • Why pea plants? • distinct heritable features, or characters (such as flower color); character variants (such as purple or white flowers) are called traits • He could control mating between plants • Small • Matures quickly

  4. Figure 11.3-3 Experiment Results: P Generation (true-breeding parents) Purple flowers White flowers • 1. Mendel produced 14 pure strainsby self-pollination • ------> P generation • 2. cross-pollinated plants w/contrasting traits • -----> F1generation • 3. self-pollinated F1generation • -----> F2generation • 4. counted and found ratios of traits F1 Generation (hybrids) All plants had purple flowers Self- or cross-pollination F2 Generation 224 white-flowered plants 705 purple-flowered plants Would these results seem strange to you if you were Mendel?

  5. Table 11.1 Good experiments have large sample sizes

  6. Figure 11.4 What we now know Allele for purple flowers Pair of homologous chromosomes Locus for flower-color gene Allele for white flowers

  7. Law of segregation • Each gamete only gets one allele for a gene

  8. law of independent assortment • - alleles for different genes distribute to gametes independently • i.e. dominant traits don't always get passed on with other 
dominant traits Are the alleles on the same chromosome or different chromosomes?

  9. Punnett Square

  10. Copy this down! For every problem, you must: 1. Definealleles 2. Define cross 3. Show work: Punnett Square 4. Box final answer

  11. monohybrid cross • A cross between individuals that are heterozygous for one character

  12. Use your white board to solve • A brown eyed man whose mother was blue-eyed marries a blue-eyed woman. • What is genotypic ratio of their potential offspring? • What are their phenotypes? • What is the probability that they will have two blue-eyed children? • Definealleles. • Define cross. • Show work/punnett square. • Box final answer.

  13. Answer: • A brown eyed man whose mother was blue-eyed marries a blue-eyed woman. • What is genotypic ratio of their potential offspring? • What are their phenotypes? • What is the probability that they will have two blue-eyed children? • Definealleles. • Define cross. • Show work/punnett square. • Box final answer.

  14. Figure 11.7 Technique How can we tell the genotype of an individual with the dominant phenotype? Dominant phenotype, unknown genotype: PP or Pp? Recessive phenotype, known genotype: pp • Possible genotypes? • testcross: breeding themystery individual with a homozygous recessive individual • If any offspring display the recessive phenotype, the mystery parent must be heterozygous Predictions If purple-flowered parent is PP If purple-flowered parent is Pp or Sperm Sperm p p p p P P Pp Pp Pp Pp Eggs Eggs P p pp pp Pp Pp Results or All offspring purple ½ offspring purple and ½ offspring white

  15. Let’s try… • Imagine your candy preference is genetic. • S = Snicker’s allele • s = Twix allele • 7 kids like Snicker’s; 1 kid likes Twix

  16. Answer: • Imagine your candy preference is genetic. • S = Snicker’s allele • s = Twix allele • 7 kids like Snicker’s; 1 kid likes Twix

  17. dihybridcross • A cross between individuals that are heterozygous for two characters

  18. Independent Assortment • Assume characters on different chromosomes

  19. Memorize this pattern:

  20. Memorize this pattern:

  21. Answer:

  22. You try: • In humans, curly hair and freckles are dominant. A 
man with curly hair whose mom had straight hair 
mates with a woman who has straight hair. Both 
parents are heterozygous for freckles. • What are the chances of having a child with straight 
hair and freckles? • What would be the chance of a child having curly hair 
and no freckles? • What about having two children with this phenotype?

  23. Answer: • In humans, curly hair and freckles are dominant. A 
man with curly hair whose mom had straight hair 
mates with a woman who has straight hair. Both 
parents are heterozygous for freckles. • What are the chances of having a child with straight 
hair and freckles? • What would be the chance of a child having curly hair 
and no freckles? • What about having two children with this phenotype?

  24. Figure 11.9  Rr Probability: Rr Segregation of alleles into eggs Segregation of alleles into sperm Sperm r R ½ ½ R R r R R ½ ¼ ¼ Eggs r r r R r ½ ¼ ¼

  25. Rule of Multiplication: “and” • What is probability of getting: • Heads and then a Tails • Heads three times in a row • A of hearts and then a Black Jack (w/replacement)

  26. Rule of Addition: “or” • What is probability of getting: • Heads ora Tails • A of hearts or a Black Jack (w/replacement)

  27. Let’s try a 2nd method for solving dihybrids: • CcFf x ccFf • What are the chances of having a child with straight 
hair and freckles? • What would be the chance of a child having curly hair 
and no freckles?

  28. Trihybrids and beyond… • AaBbCc x AABbCC • What is the probability of getting AaBbCcor AABBCC?

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