Hypothesis Testing Solving Genetics ProblemsReading AssignmentMendel’s HypothesesPhenotype of HeterozygoteHybrid VigorThe ABO Blood TypesOne RULE in doing genetics problems is that a genotype has one and only one phenotype. For each possible genotype, given the alleles you hypothesize, you must assign a single phenotype.An ABO genetics problemMore ABO genetics A Drosophila CrossA Drosophila CrossA Drosophila CrossA Drosophila CrossOur original cross under hypothesis 2A Drosophila CrossSegregation of sex chromosomes in formation of spermA Drosophila CrossComparisons of HypothesesEPISTASIS GENE INTERACTIONSA complex mouse crossF2 resultsTwo loci of coat colorTake Home ProblemVocabularyLecture 3 exam 2 UIC BioS 101 Nyberg 1Hypothesis Testing Solving Genetics ProblemsMultiple Alleles at a locusHeterozygotes with a new PhenotypeInteractions among lociLecture 3 exam 2 UIC BioS 101 Nyberg 2Reading Assignment• You have already read Chapter 13. Now it is time to use your knowledge on genetics problems.• On p.255-257 try #1, 2, & 7.• There are some practice problems posted in the Exam 2 section of the website.Lecture 3 exam 2 UIC BioS 101 Nyberg 3Mendel’s Hypotheses• There are only two alleles at a locus.• One allele is DOMINANT and the other is RECESSIVE.• The F1 has the phenotype of the dominant allele.• Alleles segregate in gamete formation.• Loci assort independently at meiosis.• Genes are not changed in heterozygotes.Lecture 3 exam 2 UIC BioS 101 Nyberg 4Phenotype of Heterozygote• The phenotype of a heterozygote is not always like one of the homozygotes.– The heterozygote can manifest attributes of both alleles.– The heterozygote can be a blend of the two homozygotes.– The heterozygote can be completely different than either heterozygote, Hybrid Vigor.Lecture 3 exam 2 UIC BioS 101 Nyberg 5Hybrid Vigor• Hybrids between lines may be more vigorous than their inbred parents.• Corn that is raised by farmers is a hybrid of a hybrid produced by seed companies. This hybrid corn has much higher yield.• Hybrids in animals, such as dogs, avoid breed specific problems, but also lack breed specific desired features.Lecture 3 exam 2 UIC BioS 101 Nyberg 6The ABO Blood TypesAlleles Genotypes PhenotypesIA IA IA AIB IA IB ABiIA iAIB IB BIB iBi i OLecture 3 exam 2 UIC BioS 101 Nyberg 7One RULE in doing genetics problems is that a genotype has one and only one phenotype. For each possible genotype, given the alleles you hypothesize, you must assign a single phenotype.Lecture 3 exam 2 UIC BioS 101 Nyberg 8An ABO genetics problemIf an individual with AB blood mates with an individual with O blood, what offspring blood types are possible and in what proportion are they expected?AB individuals produce ½ IA and and ½ IB gametes.gametes.O individuals produce all (100%) i gametes.gametes.IAIBi IB iIA iABLecture 3 exam 2 UIC BioS 101 Nyberg 9More ABO genetics • A student has type A blood. Both her parents have type A blood. What observation would tell you that BOTH of her parents were heterozygous, IAi ? • ANSWER If any of the student’s siblings had type O blood.Lecture 3 exam 2 UIC BioS 101 Nyberg 10A Drosophila Cross• What do you infer from the statement that lines X and Y are true-breeding lines?• One line had WHITE eyes, the other RED. A male from WHITE line was crossed to a female from the RED line. The F1 had RED eyes. What genetic model would you propose that explains the available facts?Lecture 3 exam 2 UIC BioS 101 Nyberg 11A Drosophila Cross• The available information suggests a situation similar to that Mendel observed for seed color.• Hypothesis #1:– One locus, two alleles (W = Red, w = White).– Red allele, W, dominant to white allele, w.• PREDICTION of F2 results.Lecture 3 exam 2 UIC BioS 101 Nyberg 12A Drosophila Cross• Hypothesis #1 (one locus two alleles) predicts that there will be two phenotypes in the F2;• RED = 0.75• WHITE = 0.25The observed results were RED =390. WHITE = 110.Lecture 3 exam 2 UIC BioS 101 Nyberg 13A Drosophila Cross• Hypothesis #2.• Some student noticed that there is a locus, white, on the X chromosome that results in a WHITE eye when homozygous.• Both male and female F1 flies have red eyes. This is possible only if the original cross was WHITE male by RED female.Our original cross under hypothesis 2Lecture 3 exam 2 UIC BioS 101 Nyberg 14Lecture 3 exam 2 UIC BioS 101 Nyberg 15A Drosophila Cross• Hypothesis 2 continued.• The RED F1 male would produce two kinds of gametes, Y and W (or w+ ).• The RED F1 females would produces two kinds of gametes, W (or w+ ) and w, in equal proportions.Segregation of sex chromosomes in formation of spermLecture 3 exam 2 UIC BioS 101 Nyberg 16Lecture 3 exam 2 UIC BioS 101 Nyberg 17A Drosophila CrossYWwWwwWWYYWWREDmaleWHITEmaleREDfemaleREDfemaleHypothesis #2. WHITE eye color due to white gene on X chromosome. Predicted F2:Lecture 3 exam 2 UIC BioS 101 Nyberg 18Comparisons of HypothesesIn both hypotheses the predicted F2 flies are expected to be 75% RED and 25% WHITE. In hypothesis #1 the RED and WHITE eye colors should appear likely among males and females. In hypothesis #2 100% of the females will have RED eyes, but 50% of the males will have RED eyes, and 50% will have WHITE eyes.Lecture 3 exam 2 UIC BioS 101 Nyberg 19EPISTASIS GENE INTERACTIONS• There are many loci that can effect eye color in Drosophila.• As is the case with the combs of chickens described in the book (p. 248), interactions among genotypes at different loci can be complex.• We will study a case of coat color in rodents.Lecture 3 exam 2 UIC BioS 101 Nyberg 20In mice a cross between a true-breeding BROWN and a true- breeding ALBINO yielded F1 individuals that were BROWN. The simple hypothesis is that there is a recessive albino allele, a, and a dominant brown allele A. This hypothesis predicts that the F2 will have 75% BROWN and 25% ALBINO.The observed results included a new phenotype, BLACK. A new phenotype is not possible with a one locus model.Thus we are forced to consider the next level of model, a two locus model.What were the observed RESULTS? N = 100BROWN 58BLACK 18ALBINO 24A complex mouse crossLecture 3 exam 2 UIC BioS 101 Nyberg 21Here is the solution that was worked out:Parents BROWN BBAA ALBINO bbaaGametes BA baF1 BbAa BROWNGametesBA Ba bA baBA BR BR BR BRBa BR A BR AbA BR BR BL BLba BR A BL AF2