01:447:380 Fall 2011
SOLUTIONS FOR PROBLEM SET 3
Additional Problems
1.
A) 1/64 = P(girl and affected) and (girl and affected) = (
½
x
¼
) x (1/2 x
¼
);
Multiply because of AND rule.
B)
1/8 = P(girl and affected) =
½
x
¼
;
identical twins arise from a single
fertilization event
C) 81/256 = P(unaffected and unaffected and unaffected and unaffected) =
¾
x
¾
x
¾
x
¾
D) 175/256 = 1 – P(none of 4 children is affected) = 1 – 81/256
E)
9/256 = P(affected and affected and unaffected and unaffected) =
¼
x
¼
x
¾
x
¾
F)
9/64 = (3!/2!1!)(1/4)
2
(3/4)
1
2.
X
2
= 0.50;
d.f.=1;
p>0.05, therefore, do not reject the hypothesis that sex
ratio at birth is 1:1.
X
2
=5;
d.f.=1;
p<0.05, therefore, reject the hypothesis that sex ratio at birth is
1:1.
3.
A) P(aa and (BB or Bb) and (CC or Cc) and dd) = 3/128;
B) 1 – [P(A_ and bb and C_ and D_) or (A_ and B_ and C_ and D_)] =
74/128;
C) If you are A_B_ccD_, what is the probability that you are AaBbccDd?
2/3 x
1 x 1 x 2/3 = 4/9
4.
A) 1; An allele (form of a gene) is present at only 1 specific location (locus) on
a chromosome
B) 2; There will be 1 locus on each of the 2 homologous chromosomes where
any of these allele could reside.
C) 2; It’s a diploid species, so 2 homologous chromosomes containing the loci
for this allele will be present.
D) 10 genotypic combinations in entire species; Let the alleles be A
1
, A
2
, A
3
,
A
4
.
Then possible genotypes include: A
1
A
1
, A
1
A
2
, A
1
A
3
, A
1
A
4
, A
2
A
2
, A
2
A
3
, A
2
A
4
,
A
3
A
3
, A
3
A
4
, A
4
A
4
5. A)
2/3 curly : 1/3 normal
B)
CyCy homozygotes are lethal
C)
90 curly and 90 normal
Chapter 3
31.
a) p(Aa and Bb and Cc and Dd and Ee) =
½
x
½
x
½
x
½
x
½
= 1/32
b)
p(Aa and bb and Cc and dd and ee) =
½
x
½
x
½
x
½
x
¼
= 1/64
c)
p(aa and bb and cc and dd and ee) =
¼
x
½
x
¼
x
½
x
¼
= 1/256
d)
p(AA and BB and CC and DD and EE) =
¼
x 0 x
¼
x 0 x
¼
= 0
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a)
The cross of two burnsi individuals produced both burnsi and pipiens offspring.
The result suggests that these individuals were heterozygous with each possessing
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 Spring '11
 GLODOWSKI
 pipiens, burnsi

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