Download BIO 208 NAME

1
BIO 208
NAME _______________________________________________
revised s08
HOMEWORK 1 Unit2: ONE GENE CROSSES
Show work for full credit. Answer on a separate piece of paper
1. When two black mice are mated, 16 of progeny are black and 5 are brown
a. Diagram the cross - show parental genotypes and phenotypes
b. What is the ratio of phenotypes in the offspring? (divide larger number by smaller).
2. Yellow seeds is a dominant characteristic in pea plants. Pure breeding pea plants for yellow
seeds were crossed with pure breeding pea plants for green seeds. The F1 generation all
exhibited yellow seeds. An F1 plant was then crossed to a green plant. Of 800 F2 plants, how
many are expected to exhibit green seeds?
3. (11.4 iGenetics) In guinea pigs, rough coat (R) is dominant over smooth coat. A roughcoated guinea pig is bred to a smooth one, giving 8 rough and seven smooth progeny in the
F1 generation. If one of the rough F1 animals is mated to its rough parent, what progeny
would you expect?
4. An autosomal recessive mutant allele causes the fruit fly, Drosophila, to exhibit a dark body
(genotype = bb). The normal color is gray. Cross a dark-bodied female fly with a gray male
fly whose father was dark-bodied. What phenotypic ratio is expected in the offspring?
5. Two phenotypically normal parents give birth to a child with sickle cell disease.
a. What is probability that their second child has sickle cell and is a girl?
b. What is the probability that 3rd child does not have disease and a boy?
6. What is the probability that two individuals with achondroplasia, a dominant disorder, in
which DD is fetal lethal (die before or shortly after birth), have child of normal height?
7. Huntington disease (HD) is a dominant disease in which symptoms begin around age 40. The
disease leads to progressive loss of brain function including dementia and uncoordinated
movements. Most people with HD are heterozygous. A woman tests positive for the HD gene
when she is in her twenties. Her husband would like to have children - he knows that he is
homozygous recessive. She maintains that because there is a chance of having a child who
will develop HD and because she herself will become ill in a few decades, they should not
have children. What is their chance of having a child who will develop HD? Show the cross.
8. Colorblindness is an X-linked trait. 10% of US males are colorblind but it is rare in females.
A woman who has a colorblind son is pregnant with the child of a colorblind man. What is
the probability that they will have a colorblind son? A colorblind daughter?
9. iGenetics question 11.27
10. iGenetics question 12.21 a ONLY (consult Box 12.1)
11. iGenetics question 12.40 a and b ONLY
Try these but do not turn in: 11.1*,11.3*, 11.6*, 11.7 *, 11.9, 11.10*, 11.26*, 11.29*, 12.29, 12.30*,
12.37*, 12.39*, 12.42*, 12.41, 12.43, 12.44 *Answers in back of book