You have three genes on the same chromosome - A, B and C. Eachgene has two alleles in a dominant/recessive relationship. Forthese genes the homozygous recessive has the mutant phenotype forthat trait, the dominant phenotype = wild type for that trait.
- allele A is dominant to a; phenotype a = mutant for trait a;phenotype A = wild type for trait A
- allele B is dominant to b; phenotype b = mutant for trait b;phenotype B = wild type for trait B
- allele C is dominant to c; phenotype c = mutant for trait c;phenotype C = wild type for trait C
Note: phenotypes can be represented by singleletters. For example phenotype A = genotypes Aa orAA; phenotype a = genotype aa. Assume thatphenotype ab =mutant phenotype for traits a andb, and wild type phenotype for traitC.
You cross an individual heterozygote for all three genes, withan individual who is homozygote recessive for all three. Out of10,000 offspring you get the following phenotypes and amounts:
- phenotype a - 98
- phenotype b - 150
- phenotype c - 4751
- phenotype ab - 4749
- phenotype ac - 147
- phenotype bc - 99
- phenotype abc - 3
- wild type - 3
Use this information to answer the following questions.
You cross an individual heterozygote for genes A, B and C, withan individual who is homozygote recessive for all three. Assumingindependent assortment for all three genes what do you expect tosee out of 10,000 offspring?
Remember:
- for all three traits wild type phenotype is dominant to mutantphenotype
- allele A is dominant to a; phenotype a = mutant for trait a;phenotype A = wild type for trait A
- allele B is dominant to b; phenotype b = mutant for trait b;phenotype B = wild type for trait B
- allele C is dominant to c; phenotype c = mutant for trait c;phenotype C = wild type for trait C
Select one:
a. Three different phenotypes among the offspring; approximately3333 offspring of each phenotype.
b. Approximately 156 offspring will have the recessive phenotypefor all three traits.
c. Approximately 2963 offspring will be wild type (dominantphenotype for all three traits).
d. Eight different phenotypes among the offspring; approximately1250 offspring of each phenotype.
