Biology 22 Problem Set 1 Spring 2011 Due Thursday, March 24th, 9:30 am
Hand in the solutions to each of the following problems. Put a box around each of your answers and show your work for partial credit. You may consult your book, lecture notes, other students and/or your instructor for assistance.
1. Fabry disease, a condition in which the lack of a lysosomal enzyme leads to nerve and kidney damage, is inherited with the recessive allele f on the X chromosome. The X-linked dominant allele F prevents the disease. Colon cancer susceptibility is inherited with the autosomal recessive allele c. The autosomal dominant allele C prevents colon cancer.
a. Maurice has colon cancer susceptibility but does not have Fabry disease. His wife Marion has Fabry disease but is not susceptible to colon cancer. Marion’s mother is susceptible to colon cancer. For Maurice and Marion, what is the probability that their first child will be a daughter with colon cancer susceptibility who does not have Fabry disease and their second child will be a son with Fabry disease and colon cancer susceptibility and their third child will be a daughter who has neither colon cancer susceptibility nor Fabry disease?
b. Out of four children born to Maurice and Marion, what is the probability that at least one will be a son with Fabry disease who is not susceptible to colon cancer?
c. Jerome has Fabry disease but is not susceptible to colon cancer. His wife Janice is susceptible to colon cancer but does not have Fabry disease. Jerome’s mother is susceptible to colon cancer. Janice’s father has Fabry disease. For Jerome and Janice, what is the probability that their first child with be either a son who has neither colon cancer susceptibility nor Fabry disease or a daughter who is susceptible to colon cancer but does not have Fabry disease?
d. Out of five children born to Jerome and Janice, what is the probability that three will be daughters with both colon cancer susceptibility and Fabry disease?
2. A prototrophic Hfr strain of E. coli with the genotype trp+ pyrC+ purB- is conjugated with an F- strain with the genotype trp- pyrC- purB+. The trp gene is known to enter last. The following numbers of recombinants were isolated:
trp+ pyrC- purB- / 44trp+ pyrC+ purB+ / 0
trp+ pyrC- purB+ / 96
trp+ pyrC+ purB- / 260
Draw a genetic map that shows the order in which these genes are arranged and the distances between them.
3. Four different Hfr strains of E. coli transfer their genes in the order given below:
Entry Time (min) / 4 / 42 / 70 / 101
Strain 2 / Gene Markers / F / C / E / D
Entry Time (min) / 8 / 20 / 60 / 91
Strain 3 / Gene Markers / B / F / A / E
Entry Time (min) / 2 / 11 / 49 / 63
Strain 4 / Gene Markers / C / A / E
Entry Time (min) / 5 / 31 / 45
Using these results, construct a linkage map of the circular E. coli chromosome. Express the gene distances in transfer time (minutes) between adjacent pairs of genes.
4. A female rabbit with hemophilia and rickets and a tail was mated to a male rabbit that did not have hemophilia or rickets but lacked a tail. The F1 females were all wild type, that is, not having hemophilia or rickets but having a tail. The F1 males had hemophilia, rickets, and tails. A cross of F1 females to F1 males produced the following offspring in the F2 generation:
Phenotype For /Number of
Hemophilia / Rickets / Tails / Males / FemalesHemophilia / No rickets / Tail-less / 13 / 0
No hemophilia / Rickets / Tail / 17 / 81
Hemophilia / Rickets / Tail-less / 2 / 0
No hemophilia / No rickets / Tail / 3 / 165
Hemophilia / No rickets / Tail / 51 / 86
No hemophilia / Rickets / Tail-less / 59 / 0
Hemophilia / Rickets / Tail / 179 / 168
No hemophilia / No rickets / Tail-less / 176 / 0
a. What are the genotypes of the original parents in this cross? Write each genotype to show which alleles are linked together on the same chromosome.
b. What are the genotypes of the F1 males and females? Write each genotype to show which alleles are linked together on the same chromosome.
c. Draw a genetic map showing the distances between theses genes. Express the distances in map units.
d. What is the degree of interference?
5. Deafness and red-green colorblindness in humans are determined by recessive alleles at X-chromosome loci that are 10 map units apart. Consider the pedigree shown below.
a. What are the possible genotypes for individual III-3? What is the probability for each possible genotype?
b. What is the probability that individual III-3 can have a colorblind son with deafness?
c. What are the possible genotypes for individual III-5? What is the probability for each possible genotype?
d. What is the probability that individual III-5 can have a colorblind son with deafness?