Principles and Practices of Genetics Lab Worksheet

Name: Principles and Practices of Genetics Lab Worksheet Analysis Directions Complete the questions below. These questions are intended to enhance critical-thinking skills by applying knowledge obtained from the lab activities into real-world challenges. • If ratios or probabilities are asked for, your answer should involve fractions or a percent. • If phenotypes are asked for, describe the traits. • If genotypes are asked for, describe alleles using the letter symbols like AA, Aa and aa (e.g., a genotypic ratio might be: 1 AA : 2 Aa : 1 aa, and a phenotypic ratio might be: 3 short :1 tall) • Remember to use capital & lowercase letters to indicate complete dominance, superscript notations (CB or CW) for incomplete dominance and IA, IB, IAB or ii for blood typing. 1. For each of the following problems a. – d., solve for the type of inheritance, and explain the rationale of your choice: a. Mice: red-eyed mouse X white-eyed mouse gives F 1: all red-eyed Inheritance is complete since all are heterozygous B b b B Bb Bb Bb Bb b. Flowers: blue-flowered plant X white-flowered plant gives F1: all pale-blue-flowered Inheritance Incomplete since all result in pale-blue flowers Tb Tb Tn TbTn TbTn TbTn TbTn Tn c. Flowers: pale-blue F1 X pale-blue F1 gives F2: i. 27 blue ii. 49 pale-blue iii. 24 white 1:2:1 ratio, Inheritance incomplete dominance DdDa x DcDa Dd Da DcDd DcDa DdDa DaDa Dc Da S20 1 Name: Principles and Practices of Genetics Lab Worksheet S20 2 Name: Principles and Practices of Genetics Lab Worksheet d. Blood Type: cross 1: type A blood X type B gives F1: i. 2 type A blood ii. 3 type AB blood iii. 1 type B blood iv. 2 type O blood Multiple alleles Ia i IaIb Ibi Iai ii Ib i **Ignore the number of each resulting blood type 2. Rough-coated guinea pigs crossed with smooth-coated ones would produce only rough-coated offspring. (RR = Homozygous Dominant, Rr = Heterozygous, rr = Homozygous Recessive). a. What results would be expected by breeding the F1 individuals? Genetic ratio is 1:2:1, Phenotype ratio is 3:1 R b. R r RR Rr Rr rr r What results would be expected by breeding one of the F1 pigs to a homozygous recessive parent? Genetic ratio is 2:2, Phenotype ratio is 2:2 R r r Rr rr Rr rr r S20 3 Name: Principles and Practices of Genetics Lab Worksheet 3. In humans, the allele that confers the ability to roll the tongue is dominant over the allele that does not confer the ability to roll the tongue. Construct a pedigree chart to answer the following questions. a. If a man who can roll his tongue and whose mother could not mates with a woman who cannot roll her tongue, what proportion of their children would be expected to be able to roll their tongues if they have a large number of children? R r r r Rr rr Rr rr b. What are the genotypes that are possible among these children? Homozygous recessive 50% and heterozygous dominant 50% 2:2 4. If two traits among flowers, dwarfism and stem color, were on the same pair of chromosomes, would you expect an F2 generation of 9:3:3:1 for a dihybrid cross? Use Mendel’s laws and your understanding of meiosis to explain your answer. Yes Dwarfism and stem color among flowers with two copies of the recessive allele are due to the accumulation of monosaccharides and excess water in seeds because of the lack of a key enzyme. 5. In fruit flies, the allele for red eyes is dominant over the allele for pink eyes. Straight wings are dominant over curled wings. Imagine that a red-eyed, straight-winged fly that is heterozygous for both traits is crossed with a fly with pink eyes and curled wings. Predict the offspring that would be produced by this cross (genotypes, phenotypes, and probability of each). RA Ra rA ra RrAa Rraa rrAa rraa RrAa Rraa rrAa rraa RrAa Rraa rrAa rraa ra ra ra RrAa Rraa Phenotype ratio is 4:4 rrAa rraa ra Genotype ratio is 4:4:4:4 Ar=50% rr=50% Ra=50% aa=50% RrAa=1/4 or 25% Rraa=1/4 or 25% rrAa=1/4 or 25% S20 4 Name: Principles and Practices of Genetics Lab Worksheet rraar=1/4 or 25% 6. Now consider a homozygous red eyed, curly winged fly with a pink eyed, heterozygous straight winged fly. Predict the offspring that would be produced by this cross (genotypes, phenotypes, and probability of each). RA RA RA RRAA RA RRAA RRAA RRAA RRAa RRAa RRAa RRAa RrAA RrAA RrAA RrAA RA Ra rA RrAa RrAa RrAa Phenotype ratio is 4:4 RrAa ra Genotype ratio is 4:4:4:4 Ar=50% rr=50% Ra=50% aa=50% RrAa=1/4 or 25% Rraa=1/4 or 25% rrAa=1/4 or 25% rraar=1/4 or 25% 7. Two parents, both with blood type A, have six children who have blood type A. One of the offspring fathers a child with blood type O. What can you tell about the genotypes of the two parents and all their offspring? Draw a pedigree chart and explain your answer. IA i IAIb IBi IAi ii IB i Most likely due to the fact that there is no blood type O children,1 parent is homozygous for IA and one is heterozygous for A S20 5 Name: Principles and Practices of Genetics Lab Worksheet 8. In some chickens, the gene for feather color is controlled by codominance. The allele for black is C B and the allele for white is CW. The heterozygous phenotype is known as erminette (black and white spotted). What is the genotype for black chickens? ____1/4____ What is the genotype for white chickens? ____1/4____ What is the genotype for erminette chickens? ___1/4_____ Two erminette chickens were crossed. Show the Punnett square. List the phenotypic and genotypic ratios of the offspring. C^wb C^bw C^w C^b C^b C^b C^wb C^wb C^b C^w C^bw C^wb 9. A black chicken and a white chicken are crossed. Show the Punnett Square. What is the probability that they will have erminette chicks? C^b C^w C^b C^w C^b C^b C^b C^w C^w C^b C^w C^w S20 6