Review work from previous class:
­ Mendel's experiment
­ monohybrid cross
­ F1 and F2 generations
­ Mendelian ration
­ Law of Segregation
Feb 17­1:21 PM
The Product Rule of Genetics
­ the product rule states that the chance of 2 or more independent events occurring is the product of their individual chances occurring alone
Ex. Coin Toss
Probability of 4 heads =1/2 x1/2 x1/2 x1/2 =1/16
Ex. Babies
P(3 boys) = 1/2 x 1/2 x 1/2 = 1/8
P(2 boys & 1 girl) = 1/2 x 1/2 x 1/2 = 1/8
P(2 girls and 1 boy) = 1/2 x 1/2 x 1/2 = 1/8
The previous events have no bearing on the following events.
Thus, just because parents have 3 boys does not mean they are due for a girl, genetics does not work that way.
Feb 17­1:24 PM
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Punnett Squares
­ used to calculate the probability of an offspring inheriting a particular trait
­ all the possible gametes for one parent are listed across the top and all the possible gametes of the other parent are listed on the side
­ a punnett square will give you a prediction of the possible outcome of a particular cross between traits from the parents
Feb 17­1:30 PM
Ex. What would be the expected outcome of a cross between a homozygous tall parent and a short parent
Possible Gametes: Punnett Square:
­ the genotypes are shown in the punnett square_________
­ they give you the phenotypes: Feb 17­1:34 PM
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Ex. 2: Do a cross showing the expected offspring on two tall pea plants. Both are heterozygous. Show the ratio of the genotype and the phenotype
Parents:
Gametes:
Feb 17­1:40 PM
Results:
Genotype Ratio:
Phenotype Ratio:
Feb 17­1:43 PM
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Ex 3: Using a test cross to determine the parental genotypes
­ A test cross is mating done to determine the genotype of the P generation (parents)
­ In pea plants tall is dominant to short. If two pea plants produce 5 tall and 5 short what are the most likely genotypes of the parents (work backward)
Likely parental genotypes:
Feb 17­1:46 PM
Readings: pages 531 ­ 534
Samples and Activities:
­ page 533: Sample Problem #'s 1,2,3
­ handout of activities
­ questions page 535 #'s 10­15
Feb 17­1:50 PM
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