SAMPLE QUESTIONS &
ANSWERS
633
, 2011 Genetics Review Course
Sample Questions & Answers
This document contains a consolidation of sample questions with the answers following each
section. All questions have been organized by category for ease of review.
Section Title
A Quantitative Genetics
B Biochemical Genetics
C Clinical Genetics
D Neurological Genetics
E Molecular Genetics
F Genetic Counseling
G Cancer Genetics
H Cytogenetics
I Prenatal Genetics
J Mendelian Genetics
K Developmental Genetics
L Genomic Medicine
,A. Quantitative Genetics Questions A1-A37
A1. Assume that 500,000 serial newborns were examined for new mutation cases of a dominant
disorder with 100% penetrance. Ten affected infants were found with unaffected parents. Which
of the following represents the calculated mutation rate?
A. 1 x 10-6
B. 2 x 10-6
C. 1 x 10-5
D. 2 x 10-5
E. 4 x 10-5
A2. A couple are both carriers for an autosomal recessive disorder. They have four children. What is
the probability that at least one child is affected?
A. 40/256
B. 81/256
C. 160/256
D. 175/256
E. 216/256
A3. What is the coefficient of inbreeding (F) for a mating of half-siblings?
A. 1/4
B. 1/8
C. 1/16
D. 1/32
E. 1/64
A4. A couple requests genetic testing for their newborn child (arrow) who is at risk of a sex-linked
recessive disorder that affects the child’s brother and uncle. A linkage study is performed using a
marker closely linked to the disease locus. There are two alleles at the marker site: A and B, and
the distance between the marker locus and the disease locus is estimated to be 5 cM. What is the
risk of this child developing signs of the disorder, assuming complete penetrance?
A. 0.0475
B. 0.0500
C. 0.0950
D. 0.0975
E. 0.1000
651
, A5. I-1 was affected with Hemophilia (Factor VIII deficiency). What is the probability that the
pregnancy (IV-4) will result in a boy affected with Hemophilia?
A. 1/4 I
1 2
B. 1/8
C. 1/9
II
D. 1/18 1 2
E. 1/36
III
1 2
IV
P
1 2 3 4
A6. A couple presents for prenatal counseling and you obtain the family history documented in the
pedigree below. They have two healthy sons and she is pregnant again. What is the approximate
probability that her fetus will be severely affected with hydrocephalus?
A. 1/5.
B. 1/8.
C. 1/10.
D. 1/20.
E. 1/32.
A7. Assume a three allele autosomal DNA polymorphism with gene frequencies of 0.50, 0.25, and
0.25. What proportion of the population will be heterozygous for these polymorphisms?
A. 4/16 (0.25)
B. 6/16 (0.375)
C. 8/16 (0.5)
D. 10/16 (0.625)
E. 12/16 (0.75)
652
ANSWERS
633
, 2011 Genetics Review Course
Sample Questions & Answers
This document contains a consolidation of sample questions with the answers following each
section. All questions have been organized by category for ease of review.
Section Title
A Quantitative Genetics
B Biochemical Genetics
C Clinical Genetics
D Neurological Genetics
E Molecular Genetics
F Genetic Counseling
G Cancer Genetics
H Cytogenetics
I Prenatal Genetics
J Mendelian Genetics
K Developmental Genetics
L Genomic Medicine
,A. Quantitative Genetics Questions A1-A37
A1. Assume that 500,000 serial newborns were examined for new mutation cases of a dominant
disorder with 100% penetrance. Ten affected infants were found with unaffected parents. Which
of the following represents the calculated mutation rate?
A. 1 x 10-6
B. 2 x 10-6
C. 1 x 10-5
D. 2 x 10-5
E. 4 x 10-5
A2. A couple are both carriers for an autosomal recessive disorder. They have four children. What is
the probability that at least one child is affected?
A. 40/256
B. 81/256
C. 160/256
D. 175/256
E. 216/256
A3. What is the coefficient of inbreeding (F) for a mating of half-siblings?
A. 1/4
B. 1/8
C. 1/16
D. 1/32
E. 1/64
A4. A couple requests genetic testing for their newborn child (arrow) who is at risk of a sex-linked
recessive disorder that affects the child’s brother and uncle. A linkage study is performed using a
marker closely linked to the disease locus. There are two alleles at the marker site: A and B, and
the distance between the marker locus and the disease locus is estimated to be 5 cM. What is the
risk of this child developing signs of the disorder, assuming complete penetrance?
A. 0.0475
B. 0.0500
C. 0.0950
D. 0.0975
E. 0.1000
651
, A5. I-1 was affected with Hemophilia (Factor VIII deficiency). What is the probability that the
pregnancy (IV-4) will result in a boy affected with Hemophilia?
A. 1/4 I
1 2
B. 1/8
C. 1/9
II
D. 1/18 1 2
E. 1/36
III
1 2
IV
P
1 2 3 4
A6. A couple presents for prenatal counseling and you obtain the family history documented in the
pedigree below. They have two healthy sons and she is pregnant again. What is the approximate
probability that her fetus will be severely affected with hydrocephalus?
A. 1/5.
B. 1/8.
C. 1/10.
D. 1/20.
E. 1/32.
A7. Assume a three allele autosomal DNA polymorphism with gene frequencies of 0.50, 0.25, and
0.25. What proportion of the population will be heterozygous for these polymorphisms?
A. 4/16 (0.25)
B. 6/16 (0.375)
C. 8/16 (0.5)
D. 10/16 (0.625)
E. 12/16 (0.75)
652
