Mendelian Genetics/The Chromosomal Basis of Inheritance-Chapter 14 and 15
1. Explain Mendel’s Law of Segregation and Law of Independent Assortment.
2. Use the rules of probability to determine the expected ratio of offspring showing two recessive traits in the
trihybrid cross (PpYyRr X Ppyyrr).
3. In corn, the trait for tall plants (T) is dominant to the trait for dwarf plants (t) and the trait for colored kernels (C)
is dominant to the trait for white kernels (c). In a particular cross of corn plants, the probability of an offspring
being tall is 1/2 and the probability of a kernel being colored is 3/4. Which of the following most probably
represents the parental genotype? Include your work to show how you derived your solution.
a. TtCc x ttCc
b. TtCc x TtCc
c. TtCc x ttcc
d. TTCc x ttCc
e. TTCc x TtCC
Incomplete Dominance
4. In radishes, the gene that controls color exhibits incomplete dominance. Pure-breeding red radishes crossed
with pure-breeding white radishes make purple radishes. What are the genotypic and phenotypic ratios when
you cross a purple radish with a white radish?
Co-Dominance
5. A man with type AB blood marries a woman with type B blood. Her mother has type O blood. List the expected
phenotype & genotype frequencies of their children.
6. The father of a child has type AB blood. The mother has type A. Which blood types can their children NOT have?
7. A woman with type A blood and a man with type B blood could potentially have offspring with what blood
types?
8. The mother has type A blood. Her husband has type B blood. Their child has type O blood. The father claims the
child can’t be his. Is he right?
9. The mother has type B blood. Her husband has type AB blood. Their child has type O blood. The father claims
the child can’t be his. Is he right?
10. The mother has type AB blood. The father has type B blood. His mother has type O blood.
Sex-Linked
11. The genes for hemophilia are located on the X chromosome. List the possible genotypes and phenotypes of the
children from a man normal for blood clotting and a woman who is a carrier. (HINT: You have to keep track of
what sex the children are!)
Pedigree Analysis
12. What is a pedigree? Explain what they show, indicate male and female symbols and how it is determined who is
affected.
Recombination frequency
13. Compare recombination of linked genes and unlinked genes. Explain their significance.
14. Determine the sequence of genes along a chromosome based on the following recombination frequencies: A-B,
8 map units; A-C , 28 map units, A-D, 25 map units; B-C, 20 map units; B-D, 33 map units.