Download IB Bio Year 1 - Inglemoor High School

IB Bio Year 1 - Inglemoor High School
LINKED GENES PROBLEM SET – tomatoes. fruit flies, and… chickens!
Directions: Work out these problems in your journal, using careful, neat work. Circle the answers!
1. In tomatoes, vine height and fruit shape are linked. Tall vines are dominant to dwarf vines, and round fruit
(tomatoes) is dominant to pear-shaped tomatoes. When a dwarf tomato plant with pear-shaped tomatoes is crossed
to a true-breeding tall tomato plant with round tomatoes, all the first generation offspring are tall with round
tomatoes. When these first-generation plants are subjected to a test cross with the parent dwarf pear-shaped tomato
plant, these progeny are obtained:
229 tall, round
23 tall, pear-shaped
27 dwarf, round
221 dwarf, pear-shaped
a) Diagram the linkage groups of all the tomato plants in this problem (parents, F-1, and test cross
offspring)
b) Calculate % crossover between the height and shape genes.
c) How far apart are these two genes?
2. In Drosophila, a gene for eye color (wild-type red is dominant to vermillion) and wing shape (wild type long is
dominant to cut) are linked and both are on the X chromosome. Use the symbols + and v for the eye color alleles,
and + and c for the wing shape alleles. A male fruit fly with vermillion eyes and cut wings is mated to a red-eyed,
long-winged female that is heterozygous for both genes. The following progeny result:
426 cut, vermillion
69 cut, red
61 long, vermillion
444 long, red
a) Diagram the linkage groups of the parents and the above progeny.
b) What is the % crossover between these two genes?
c) How far apart are these two genes?
3. Assume that, in chickens, feather color and amount of down are linked. The allele for silver plumage (S) is at
locus 12.0, and the allele for light down (Li) is at locus 28.0 on the same chromosome. Both alleles are dominant
over their corresponding wild-type alleles. What percent of the various types of progeny would be expected from this
cross:
S+
Li
S+
Li+
____________
___________
____________
x
___________
S
Li+
S+
Li+