BIOL 101 1nd Edition Lecture 15 Outline of Last Lecture I. Law of Equal SegregationII. AllelesIII. Single Gene CrossesOutline of Current Lecture I. ApplicationII. PedigreesIII. Problems involving PedigreesCurrent LectureThinking like a geneticist and applying what you know: In fruit flies, a mutation leads to small wings. Is this dominant or recessive? How can you find out? The cross that you might do: A purebreeding fruit fly with small wings was crossed to a purebreeding fruit fly with normal wings andall the progeny had small wings. When the F1 generation was interbred, 400 F2 flies were counted. 305 had small wings and 95 had wild type wings.Which allele is dominant? smallWrite the genotypes of the F1 flies. Write the genotypes of the F2 flies.Aa (small wings A, wild wings AA (small wings), Aa (small wings), aa (wild wings)In this example the mutant allele is not recessive to the wildtype allele. The wildtype allele is NOT always the dominant allele!I. Pedigrees allow us to determine the pattern ofinheritance of a familial disorder. i. Recessive Disorders: 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.Skip generations, the colored in ones are the affected. Children with unaffected parents can be affected.ii. Dominant Disorders:Present in every generation. 1. Is the genetic disorder represented in the pedigree to the right recessive or dominant? (Hint- Think about how we defined these terms.)2. How do you know?It skips generations and child with disorder is born to unaffected parents. What are the probable genotypes of various individuals in the pedigree? For example, what is the genotype of I-2? II-4?Important assumption: the disease allele is rare in the population so people marrying into the family are assumed to not have the disease allele.II. The rule of multiplication can be used to determine the probability that a child has arare genetic disorder.i. Rule of multiplication – the probability that two independent events will occur is the product of their individual probabilities. PRACTICE! Determine the probability that if individuals III-1 and III-2 marry, their child will have the autosomal recessive disease represented in thispedigree.Aa, Aa, Aa, Aaaa, AA or Aa, Aa or AA AA, AA, Aa or AA, aaAa or AA, Aa or AAAA or AaApproaching the problem.1. Calculate the probability that the unborn child’s father carries the disease allele. (probability that the unborn child’s grandfather is a carrier_2/3_) x (probability that the unborn child’s father is a carrier____1/2____) = ____1/3_______.2. Calculate the probability that the unborn child’s mother carries the disease allele. (probability that the unborn child’s grandmother is a carrier __1___) x (probability that the unborn child’smother is a carrier___1____) = ____1____.3. The probability that if III-1 and III-2 marry, their child will have the autosomal recessive disorder = 1/4(probability that the father will carry the disease allele___1/3______) x (probability that the mother will carry the disease allele____1_____) x (probability that the unborn child will have the disease__1/4_______)Drum roll please… THE
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