Download Problems 10-3

BS 50—Genetics and Genomics
Week of Oct 3
Additional Practice Problems for Section
1. In the following cross, all genes are on separate chromosomes. A is dominant to a, B is
dominant to b and D is dominant to d.
A/a ; B/B ; d/d X A/a ; b/b ; D/d
What proportion of the progeny will be
A/a?
phenotypically A?
phenotypically a?
phenotypically B?
b/b?
D/d?
a/a ; d/d?
A/a ; D/d?
phenotypically A D?
a/a ; B/b; d/d?
A/a ; B/b ; D/d?
phenotypically a B D?
2. This human pedigree describes the inheritance of a rare single gene hereditary disease. The #
and * symbols indicate individuals addressed in the problem; these symbols do not indicate
anything about the genotype.
#
a. What possible genotype(s) does the unaffected female denoted with (#) have?
*
b. What possible genotype(s) does the unaffected male denoted with an asterisk ( ) have?
*
Unaffected male is a polygamist with three wives. One of his wives is homozygous for the
dominant allele, another is homozygous recessive, and the third is heterozygous. He has four
children by each of the wives, and none of the children are identical twins. All twelve children
are unaffected.
c. What is male
*’s most likely genotype? Why? Be quantitative with your answer.
d. Are you certain of the genotype in part c? Why or why not?
3. A diploid organism has a somatic chromosome number of 10.
a. How many chromosomes are present per cell at the following stages of cell division:
Metaphase of Mitosis
________________
Metaphase I of Meiosis
________________
Metaphase II of Meiosis
________________
b. A unique labeling technique is used such that all paternally-derived centromeres are
labeled blue and all maternally-derived centromeres are labeled red. What is the
probability that a gamete from an individual stained with this labeling technique will
contain only red centromeres? (you can leave your answer in the form of a reduced
fraction or equation)
c. What is the probability that a gamete from an individual stained with this labeling
technique will contain exactly 3 blue and 2 red centromeres? (you can leave your answer
in the form of a reduced fraction or equation)
4. (18 pts) The following questions refer to the pedigree below. Assume that all individuals
marrying into the pedigree are homozygous normal unless there is evidence that indicates
otherwise.
A) Is this trait dominant or recessive? Explain.
B) Is this trait autosomal or sex–linked? Explain.
C) What is the probability that the first child born to individuals R & S will be affected?
5. (18 pts) Complete the following statements using as many of the choices as are appropriate:
A) mitosis
B) meiosis I
C) meiosis II D) none (not mitosis nor meiosis I or II)
i.) The spindle apparatus is present in cells undergoing ___________________.
ii.) Reduction in ploidy occurs at ___________________.
iii.) Pairing of nonhomologous chromosomes is a feature of ___________________.
iv.) Centromeres divide during ___________________.
v.) Sister chromatids divide during ___________________.
6. You have one strain of moth that is pure-breeding for light wings and another strain that is
pure-breeding for dark wings. You cross a light-winged female with a dark-winged male and
find that all F1 progeny have dark wings. You then cross the F1 individuals to each other and
find that all the males have dark wings, half the females have light wings, and half the females
have dark wings.
Explain this result.
What result would you expect for the F1 and F2 generation from the reciprocal cross (darkwinged female crossed to a light-winged male)?