Biology 303 Midterm, Fall 2007
1. If a family plans to have five children, what is the probability that four of them would
be girls?
2. Assume that you have a garden and some pea plants have solid leaves and others have
striped leaves. You conduct a series of crosses (a through e) and obtain the results given
in the table.
Cross
(a)
(b)
(c)
(d)
(e)
Progeny
solid X striped
solid X solid
striped X striped
solid X solid
solid X striped
solid
striped
55
36
0
92
44
60
0
65
30
0
Define gene symbols and give the possible genotypes of the parents of each cross.
3. The genes for garnet eyes and forked bristles are 12.5 map units apart on the X
chromosome in Drosophila melanogaster. Both genes are recessive. A cross is made
between a garnet-eyed female and a forked-bristled male. (a) If 200 offspring from this
cross were obtained, present the expected number, sex, genotype, and phenotype in each
class of the F1. (b) If the F1 offspring were crossed to produce 800 flies of an F2
generation, present the expected number, sex, and phenotype in each class. Assume 20%
recombination occurs between.
4. A corn plant known to be heterozygous at three loci was testcrossed. The following
progeny were obtained:
+++
abc
+bc
a++
++c
ab+
+b+
a+c
455
470
36
33
36
35
460
475
Determine the gene arrangement, linkage relationships, and map distances.
5. A female fruit fly was mated to a wild type male and the following progeny were
obtained:
Female
+++
2000
Male
+++
abc
+bc
a++
++c
ab+
+b+
a+c
3
1
839
825
86
90
81
75
Determine the gene arrangement, linkage relationships, map distances, and coefficient of
coincidence.
6. The following results are ordered tetrad pairs from a cross between strain p+ and strain
+q:
1
p+
p+
+q
+q
55
2
p+
pq
++
+q
4
3
pq
pq
++
++
3
Tetrad Class
4
+q
p+
p+
+q
6
5
p+
++
pq
+q
21
6
pq
++
pq
++
5
7
p+
+q
pq
++
3
They are summarized by tetrad classes.
a) Calculate the gene-centromere distance for each locus.
b) Calculate the distance between the two linked loci.
c) Draw a linkage map, including the centromere.
7. Ten female guppies had the following numbers of liveborn offspring in their first litter:
21, 19, 23, 14, 19, 28, 30, 26, 17, and 13. Calculate the mean, variance (s2), and the
standard deviation (s) of the litter size for these data.