WORKING GENETICS PROBLEMS You absolutely have to know what the words mean: phenotype genotype heterozygote homozygote gene locus allele recessive dominant linked sex linked (X linked recessive) zygote gamete test cross P generation, F1, F2 And you have to know the answers to these questions: How many alleles for each gene in each adult? How many alleles for each gene in each gamete produced by the adult? If G = Yellow and g = Green, what are the possible genotypes for adults? What are the possible phenotypes? What are the possible genotypes for gametes? Finally, you must read each question carefully – what information is given to you? What is being asked of you? If a question asks you for the phenotypes of the F2 generation and you supply an answer like “WwGg” you have not given a phenotype. Here are some exercises to do together if you have a study group: 1. Do monohybrid cross (P generation = AA x aa) - note ratio of phenotypes in F2 generation 2. Cross a heterozygote with a homozygous recessive - note ratio 3. Bring in another locus – what kind of genotypes are possible when two loci are involved? If G = Yellow and g = Green, and at another locus H = hairy and h = hairless, what are the possible genotypes for adults? What are the possible phenotypes? What are the possible genotypes for gametes? 4. Do a dihybrid cross (P generation = AABB x aabb) and note the ratio of offspring in the F2 generation. 5. Do a test cross between a double heterozygote and a double recessive. Note ratio. 6. Do a cross involving incomplete dominance. 7. What does sex linked mean? 8. What are the possible genotypes for a female for red-green colorblindness? 9. What are the potential genotypes for a male? 10. What patterns of inheritance show that a trait is sex-linked? 11. What patterns of inheritance show that two different genes are linked?