Name ___________________
PID ___________________
Section (circle):
1- Karen
2- Robyn
3- Veronica
CSS 350
Homework Assignment #5 (version 2)
Assigned
1/17/01
Due
1/24/01
Given:
F1 genotype AaBb.
Gene action model 1: the two loci do not show epistasis. Gene action within a locus is
additive. Each uppercase allele contributes 10 units of enzyme X, and each lowercase
contribute 0 units of enzyme X. So AAbb and aaBB and AaBb all have 20 (not 40 as the
original version indicated) units of enzyme.
Gene action model 2: A and B code for enzymes in a pathway that creates a pigment. The
loci exhibit duplicate recessive epistasis and the only genotype that produces pigment is
aabb.
Gene action model 3: A codes for plant height and A- is tall and aa is short. B codes for
flower color and B- is red and bb is white.
1) Show the gametic genotypes and their associated probabilities (i.e., the frequency
distribution of gametic geotypes) that are produced by the F1 described above.
Assume the genes are unlinked.
2) Show the F2 genotypes and their associated probabilities that result from selfing the
F1 described above. Assume the genes are unlinked.
3) Show the phenotypes and associated probabilities of the result from selfing the F1
described above assuming gene action model 1.
4) Show the phenotypes and associated probabilities of the result from selfing the F1
described above assuming gene action model 2.
5) Show the phenotypes and associated probabilities of the result from selfing the F1
described above assuming gene action model 3.
Page 1 of 2
Name ___________________
PID ___________________
Section (circle):
1- Karen
2- Robyn
3- Veronica
Given: a plant species has a genome with two chromosomes, one short and one long
(N=2 and 2N=4). The short chromosome has the “A” locus. The long chromosome
has the “B” locus on one arm, and “C” loci on the other arm.
A plant with genotype AAbbCC is crossed to a plant with genotype aaBBcc. In the
following questions (6 and 7) always label the chromosomes/chromatids with the
correct allelic symbol for each locus.
6) Diagram the chromosomes of the gametes of the parents and the zygote
resulting from this cross: AAbbCC x aaBBcc .
7) Diagram mitosis of the zygote.
Assume that 4 unlinked loci each influence plant height. In each case, the capital
case allele adds 10 cm to plant height, and the small case allele adds 5 cm to plant
height. Gene action within and between loci is additive, so the height of a plant
equals (5 x # of lower case alleles ) +(10 x # of upper case alleles). A completely
genotype that is homozygous for smaller case alleles at all loci (aabbccdd) has a
plant height of 40cm, and a genotype that is homozygous for upper case alleles at
all loci (AABBCCDD) has a plant height of 80cm. Aabbccdd or any other genotype
with only one capital allele at only one locus has a height of (5cm x 7 lower case)
+(10 cm x 1 upper case)=45 cm.
8) List the phenotypic frequency distribution (phenotypes and frequencies) for the
F2 progeny created by selfing this F1: AaBbCcDd.
9) Create a histogram for the phenotypic frequency distribution from question 8.
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