BOLOGY 107 Lecture 22 Outline of Last Lecture I Mendelian Genetics a Polymorphism b Genetics c Problems with Mendel II Outline of Current Lecture III Genetics a Punnett square b Laws of independent assortment c Probability d Test cross Current Lecture Genetics 1 Punnett square a Table used to predict possible outcomes from a genetic cross i Place the parents genomes along the axes fill in for progeny ii Deduce phenotype ratio 2 Laws of independent assortment a Dihybrid cross cross involving two traits 1 Example RRYY round yellow pea and rryy wrinkled green pea ii Random assortment of all traits leading to a 9 3 3 1 ratio 1 Genes for different traits assort randomly during gametogenesis 2 All possible combinations of phenotype can be seen 3 Distinct trait combinations are seen in children that are not seen in parents round green pea 3 Probability a Likelihood that a specific possible outcome will occur i specific outcome total of outcomes b Addition rule probability of multiple outcomes is the sum of the probabilities for each event i Either or result statements These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute c Multiplication rule probability of independent events occurring together is the product of each independent event i And then result statements d Can use either punnett square or probability rules to get basic ratios i Easier to use probability rules if more than two traits are being considered 4 Test cross a Experimental cross to determine the genotype of a parent displaying the dominant phenotype i Cross with the homozygous recessive 1 If the parent is homozygous dominant then all progeny will show the dominant phenotype 2 If the parent is heterozygous recessive then there will be some progeny showing the recessive phenotype
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