Файл: Genetics [BRS].pdf

33.

What is I-1’s risk to be a carrier?

(A)

1 (100%)

(B)

2/3 (66%)

(C)

1/2 (50%)

(D)

1/4 (25%)

(E)

0

34.

What is II-2’s risk to be a carrier?

(A)

1 (100%)

(B)

2/3 (66%)

(C)

1/2 (50%)

(D)

1/4 (25%)

(E)

0

35.

What is the chance for their next child

(II-3) to be affected?

(A)

1 (100%)

(B)

2/3 (66%)

(C)

1/2 (50%)

(D)

1/4 (25%)

(E)

0

36.

Which of the following statements

applies to the use of ultrasonography in
pregnancy?

(A)

Level II ultrasound is optimally 
done between 10–12 weeks of 
pregnancy.

(B)

All babies with Down syndrome will
show the “banana sign” and the “lemon
sign.”

(C)

Ultrasonography detects 95% of major
structural abnormalities but can miss
small defects.

(D)

Ultrasonography has no risk to mother or
baby.

37.

Which one of the following statements

regarding prenatal diagnosis is accurate?

(A)

Diagnostic testing like CVS or amnio-
centesis is the definitive way to diag-
nose a chromosome problem prior to
birth.

(B)

One of the benefits of CVS or amnio-
centesis is that it can be used as a
screening test to determine the predis-
position for multifactorial diseases of
adulthood.

(C)

One of the major advantages of amnio-
centesis over CVS is that it can be per-
formed in the first trimester, although
there is a higher risk of miscarriage with
amniocentesis. 

(D)

CVS screens for open neural tube defects
but amniocentesis does not.

The following is a pedigree for a family with
the darkened individuals being affected with
hemochromatosis:

38.

What is the likelihood that the mother is

a carrier of a hemochromatosis mutation?

(A)

0%

(B)

25%

(C)

50%

(D)

100%

39.

Which if the following would be an

appropriate indication for offering prenatal
diagnosis?

(A)

A woman who will be 40 years old at
delivery.

(B)

A fetus determined to be male by ultra-
sonography.

(C)

A woman with a fourth-degree relative
with cleft lip and palate.

(D)

A woman who is pregnant by her fifth
cousin.

The following pedigree applies to questions 40–42.

(A)

pedigree A

(B)

pedigree B

(C)

pedigree C

(D)

pedigree D

Pedigree A

Pedigree B

Pedigree C

Pedigree D

Comprehensive Examination

205

LWBK274-COMP_201-227.qxd  06/02/2009  04:56 PM  Page 205 Aptara

40.

Which pedigree best represents the

mode of inheritance for an X-linked domi-
nant condition?

41.

Which pedigree best represents the

mode of inheritance for an X-linked reces-
sive condition?

42.

Which pedigree best represents the

mode of inheritance for an autosomal reces-
sive condition?

The following pedigree applies to the next
question.

43.

What is the most likely mode of inheri-

tance?

(A)

autosomal dominant

(B)

autosomal recessive

(C)

X-linked recessive

(D)

X-linked dominant

The following pedigree applies to the next
question.

44.

What is the least likely mode of inheri-

tance?

(A)

autosomal dominant

(B)

X-linked recessive

(C)

mitochondrial

(D)

X-linked dominant

45.

Which one of the following is an accurate

statement?

(A)

Germline mosaicism can explain the rare
occurrence of multiple affected siblings
born to unaffected parents where one
parent carries the disease-causing muta-
tion only in their gametes.

(B)

The same disease phenotype can be
caused by mutations in different genes at
different places in the genome, which is
called allelic heterogeneity.

(C)

A person with a genetic disease showing
more severe symptoms than their affected
sibling is an example of penetrance.

(D)

Different mutations in the cystic fibrosis
gene causing varying severity of the dis-
ease would be an example of locus het-
erogeneity.

For questions 46–48, match the diagnostic pro-
cedure with the appropriate description.

(A)

done at 10–12 weeks, 1%–2% risk of com-
plication

(B)

done at 15–18 weeks, 0.5% risk of compli-
cation

(C)

Rh isoimmunization management

(D)

done at 5–6 weeks, 15% risk of
complication

46.

Amniocentesis

47.

Cordocentesis 

48.

CVS

49.

Which of the following statements about

prenatal diagnosis is accurate?

(A)

CVS should be offered if there is an ele-
vated maternal serum AFP.

(B)

Screening tests are useful to screen at
risk populations and eliminate their risk
if the screen is negative.

(C)

Amniocentesis is recommended if there is
a history of neural tube defects in a family.

(D)

Cordocentesis is useful for assessing
hematologic status or infection in the
fetus, but the cells cannot be used for
fetal karyotyping.

50.

Thus far, two genes have been found that

can cause autosomal dominant breast can-
cer (one on chromosome 13 and one on
chromosome 17). This is best described as
an example of which of the following?

(A)

linkage

(B)

allelic heterogeneity

(C)

synteny

(D)

linkage disequilibrium

(E)

locus heterogeneity

51.

An infant who appears normal until 6

months of age but then develops symptoms
of progressive weakness and loss of motor
skills with decreased attentiveness and an
increased startled response most likely has
which one of the following?

(A)

metabolic disorder involving an amino
acid pathway

206

Board Review Series Genetics

LWBK274-COMP_201-227.qxd  06/02/2009  04:56 PM  Page 206 Aptara

(B)

metabolic disorder involving a degrada-
tion pathway

(C)

metabolic disorder involving a carbohy-
drate pathway

(D)

metabolic disorder involving glycogen
storage 

52.

Which one of the following clinical signs

is not indicative of an inborn error of metab-
olism?

(A)

metabolic acidosis

(B)

unusual odor in urine/sweat

(C)

vomiting and lethargy in an infant

(D)

accelerated growth in a child

(E)

mental retardation

53.

A 2-week-old baby is admitted to the

emergency room with a history of vomiting,
no interest in feeding, and lethargy. She had
been an 8-pound term baby with no neona-
tal problems. Which one of the following lab-
oratory studies is not likely to help deter-
mine the diagnosis?

(A)

blood glucose

(B)

blood gas

(C)

chromosome karyotype

(D)

plasma ammonium

(E)

liver function studies (bilirubin, 
AST, ALT)

54.

Besides microdeletions, which one of the

following mechanisms is known to cause
Prader-Willi syndrome?

(A)

chromosome duplication

(B)

translocation

(C)

uniparental disomy

(D)

autosomal trisomy

(E)

autosomal monosomy

55.

It has been suggested that schizophrenia

is more severe and has an earlier age of onset
in the more recent generations of schizo-
phrenia families. If so, this would be an
example of which one of the following?

(A)

the two-hit model

(B)

imprinting

(C)

delayed age of onset

(D)

anticipation

(E)

increased numbers of mutagens in more
recent generations

56.

Of the following, which statement is

most applicable to the group of diseases
described as “cancers”?

(A)

All cancers are inherited.

(B)

Most cancers are caused by environmen-
tal effects.

(C)

Most cancers are caused by chromosome
translocations.

(D)

All cancers have a genetic component.

57.

The mode of action of inherited cancers

such as retinoblastoma is best described as
which one of the following?

(A)

autosomal recessive

(B)

autosomal dominant

(C)

X-linked recessive

(D)

X-linked dominant

58.

You examine a child in the newborn

nursery whom you suspect has trisomy 21.
Which one of the following tests would you
order to confirm the diagnosis?

(A)

maternal serum AFP

(B)

cytogenetic analysis

(C)

DNA sequencing

(D)

neonatal genetic screening

59.

Which one of the following statements is

most applicable to the human genome?

(A)

Humans have more chromosomes 
than any other organism examined to
date.

(B)

The human genome is composed of
100,000 genes and that is the highest
number of genes seen in any organism
examined to date. 

(C)

The human genome is composed of the
greatest amount of non-coding DNA of
any organism examined to date. 

(D)

The human genome has approximately
the same number of genes as the round-
worm, Caenorhabditis elegans.

60.

The town of Lake Maracaibo, Venezuela

was settled by a few families. There are a
larger proportion of people affected by
Huntington disease in the town than in the
general population. One possible explana-
tion for this is which of the following?

(A)

selection against heterozygotes

(B)

the founder effect, or genetic drift

(C)

something in the water

(D)

selection against homozygotes

61.

The incidence of hemophilia B, an X-

linked recessive disorder, is approximately 1
in 20,000 males. What is the frequency of the
disease gene?

(A)

0.01

(B)

0.002

(C)

0.0004

(D)

0.00005

Comprehensive Examination

207

LWBK274-COMP_201-227.qxd  06/02/2009  04:56 PM  Page 207 Aptara

62.

A couple comes to see you because the

wife has been found to be a carrier of a bal-
anced reciprocal translocation between the
long arms of chromosomes 4 and 10. They
have no children and have been trying for 15
years. They want to know what this cytoge-
netic diagnosis means for their hope of hav-
ing children. Which one of the following best
summarizes what you will tell them? 

(A)

They can never have children.

(B)

They are at risk for infertility and that is
most likely the cause of their lack of suc-
cess in conceiving.

(C)

Any children they have will be abnormal.

(D)

The translocation is clinically irrelevant.

63.

A discrete group of birth defects that are

the result of a single cause is known as which
one of the following?

(A)

an association

(B)

a deformation

(C)

a syndrome

(D)

a disruption

64.

The causation of three forms of dwarfism,

a craniofacial syndrome, and isolated cran-
iosynostosis by mutations in the FGFR3 gene
is known as which one of the following?

(A)

allelic heterogeneity

(B)

a compatible pathogenic mechanism of
teratogenesis

(C)

a defect in hypertrophy of existing cells
and tissues

(D)

an extrinsic developmental defect

65.

You request a cytogenetic study on a

patient who you suspect has Prader-Willi
syndrome. The lab report comes back stating
that FISH with DNA probes specific to the
Prader-Willi/Angelman locus have revealed
that the region is deleted in your patient. You
know that the deletion is thus on which one
of the following?

(A)

the maternal chromosome 15

(B)

the paternal chromosome 15

(C)

the maternal chromosome 22

(D)

the paternal chromosome 22

66.

A pregnant female comes to your clinic

because of a family history of Duchenne
muscular dystrophy (DMD) in her maternal
uncle. He was the only person affected in her
family. Your patient is an only child and this
is her first pregnancy. What is her chance to
have a fetus that is affected with DMD?

(A)

1/8

(B)

1/12

(C)

1/16

(D)

1/24

67.

Which of the following statements is

accurate in regards to prenatal diagnosis?

(A)

Low AFP, high HCG, and low unconju-
gated estriol (uE3) on a second trimester
triple screen indicates an increased risk
for fetal Down syndrome.

(B)

Chorionic villus sampling is less risky
and more accurate for fetal chromosome
abnormalities than amniocentesis.

(C)

First trimester maternal serum AFP
screening is more accurate for 
detecting fetal trisomy 21 than second
trimester amniocentesis with fetal
karyotyping.

(D)

It is standard of care to offer pregnant
women of any age CVS.

68.

Although conventional cytogenetic stud-

ies should always be performed, fluorescent
in situ hybridization (FISH) with the appro-
priate DNA probe is the definitive test for
which of the following?

(A)

Klinefelter and Turner syndromes

(B)

Williams and DiGeorge syndromes

(C)

myotonic dystrophy and Fragile X syn-
dromes

(D)

neurofibromatosis and spina bifida

69.

Which one of the following statements

regarding neural tube defects is most appli-
cable?

(A)

Anencephaly is the most severe form of
neural tube defect.

(B)

A low maternal serum AFP can indicate
an increased risk for a fetal open neural
tube defect.

(C)

Isolated neural tube defects usually fol-
low an X-linked recessive pattern of
inheritance.

(D)

The prognosis for a neural tube defect
depends on the age of the mother at con-
ception.

70.

The main risk for children born to inver-

sion carriers is the chance of which of the
following?

(A)

Down syndrome

(B)

duplications or deletions

(C)

chronic myelogenous leukemia

(D)

Robertsonian translocations

208

Board Review Series Genetics

LWBK274-COMP_201-227.qxd  06/02/2009  04:56 PM  Page 208 Aptara

71.

Which one of the following statements is

applicable to a 45,X karyotype?

(A)

Patients with a 45,X karyotype have a
male phenotype.

(B)

Patients with a 45,X karyotype are
severely mentally retarded.

(C)

Most conceptions with a 45,X karyotype
spontaneously abort.

(D)

A 45,X karyotype is associated with Down
syndrome.

72.

Mutations in different autosomal reces-

sively inherited genes may result in leukemia
in individuals with Fanconi anemia. This is
an example of which of the following?

(A)

locus heterogeneity 

(B)

allelic heterogeneity

(C)

genotype-phenotype correlation

(D)

de novo mutations

(E)

variable expressivity

73.

The balanced reciprocal translocation

between chromosomes 9 and 22 with break-
points at q34 and q11.2, respectively, is the
leukemogenic event in the chronic myeloge-
nous leukemia (CML). Specifically, this
translocation causes leukemia by which of
the following mechanisms?

(A)

fusing proto-oncogenes and thus activat-
ing them

(B)

disrupting a tumor suppressor gene in
the breakpoint cluster region (BCR)

(C)

deleting the proto-oncogenes ABL and
BCR

(D)

deleting tumor suppressor genes

74.

Which of the following is a second-

degree relative?

(A)

great-grandchild

(B)

brother

(C)

maternal cousin

(D)

paternal second cousin

(E)

half-brother

75.

Mrs. X comes to you for genetic counsel-

ing. She is pregnant with her 2nd child, a
cytogenetically normal male by amniocente-
sis. Her mother had 2 brothers with hemo-
philia A and one normal brother. The patient
has no brothers. What is the risk for this male
fetus to have hemophilia A?

(A)

1/4

(B)

1/8

(C)

1/16

(D)

1/24

76.

A woman comes to genetic clinic

because her MSAFP triple screen is positive
for Down syndrome. What diagnostic test
would be the most appropriate to offer her?

(A)

chorionic villus sampling (CVS)

(B)

amniocentesis

(C)

level II ultrasound

(D)

preimplantation genetic diagnosis (PGD)

77.

Regarding autosomal dominant suscepti-

bility syndromes: if a family member with a
known mutation carrier has a 12.5% chance
of inheriting the mutation, then this relative
is which one of the following?

(A)

first-degree relative

(B)

second-degree relative

(C)

third-degree relative

(D)

fourth-degree relative

(E)

fifth-degree relative

78.

What is the chance that the fetus in this

family is affected with this X-linked recessive
disease? The mother is a known carrier for
hemophilia A. 

(A)

1

(B)

1/2

(C)

1/4

(D)

2/3

79.

TPMT is an enzyme involved in the

metabolism of thiopurine drugs. 1 in 300
(0.003) individuals are homozygous for a null
mutation which causes them to have severe
adverse reactions when they are given this
class of drugs. If you are offered a test which
has a sensitivity of 95% and a specificity of
99% to detect the individuals with a null
mutation, in a population of 20, 000 people,
how many people would be really affected and
how many people would the test call positive? 

(A)

60 really affected and 257 reported positive

(B)

60 really affected and 116 reported positive

(C)

60 really affected and 57 reported positive

(D)

60 really affected and 60 reported positive

= affected

= carrier

P

Comprehensive Examination

209

LWBK274-COMP_201-227.qxd  06/02/2009  04:56 PM  Page 209 Aptara