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80.
Maternal serum alpha-fetoprotein
screening is routinely offered to pregnant
women in the second trimester. Which of the
following options is an appropriate action
for follow-up?
(A)
Offering chorionic villus sampling to a
woman whose maternal serum AFP
(MSAFP) shows an increased risk for
Down syndrome.
(B)
Recalculating the screening because the
ultrasound altered the dating by 7 days.
(C)
Offering amniocentesis with ultrasonog-
raphy for a woman whose MSAFP indi-
cates an increased risk for open neural
tube defects.
(D)
Deferring amniocentesis for a woman
who will be 37 at delivery because her
MSAFP was negative, which eliminates
her risk.
81.
There are several clinical features used to
identify kindreds with familial cancer syn-
dromes. Which of the following statements is
most predictive of familial risk?
(A)
environmental exposures, such as smok-
ing, in family members with cancer
(B)
your patient’s current age
(C)
paternal history of cancer
(D)
presence of other genetic disorders in the
same family
(E)
proband with multiple cancers
82.
The frequency of an allele for an autoso-
mal dominant disorder in a population is
0.0001. What is the frequency of the disorder
in the population?
(A)
0.01
(B)
0.02
(C)
0.0001
(D)
0.0002
83.
One of your patients, a 25-year-old
woman with no health problems, has just
learned that her sister is the carrier of a 14;14
Robertsonian translocation. The patient
desires testing and wishes to know what it will
mean to her future plans of having children if
she is also found to be a carrier. You tell her:
(A)
She has a 15% risk of having a child with
trisomy 14.
(B)
She has a 5% risk of having a child with
monosomy 14.
(C)
She is at risk for infertility.
(D)
The translocation will have no effect on
her ability to have children.
84.
The risk that a father carrying a mito-
chondrial gene mutation will pass the muta-
tion to his son is:
(A)
100%
(B)
50%
(C)
25%
(D)
0%
85.
In a family where there is bilateral cleft
lip and palate, the recurrence risk would be
(fill in the word or phrase from choices
below) in a family where there is cleft palate
only.
(A)
less than
(B)
greater than
(C)
the same as
(D)
60% greater than
86.
Sally is a carrier of the most common
mutation found in the autosomal recessive
disease, cystic fibrosis (CF), which is the
delta F508 mutation on the long arm of chro-
mosome 7. Sally and Ted’s first child is found
to have CF shortly after birth. Ted is tested
and found to also be a carrier of this muta-
tion. What is the risk of having another child
with CF?
(A)
10%
(B)
25%
(C)
50%
(D)
100%
87.
In a chromosome inversion, what can be
said about the genes on the inverted piece of
the chromosome?
(A)
they are all autosomal dominant genes
(B)
the genes are in reverse order on the
chromosome
(C)
the genes have been translocated to
another chromosome
(D)
they form a ring chromosome
88.
Which one of the following is the kary-
otype of a patient with a normal phenotype?
(A)
45,X
(B)
46,XY, with a Robertsonian translocation
between chromosomes 13 and 21
(C)
47,XXY
(D)
45,XX, with a Robertsonian translocation
between chromosomes 13 and 21
89.
Which of the following is the best
estimate of the chance that a child produced
by the union of a female carrier of a 21;21
Robertsonian translocation carrier and a
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karyotypically normal male will have Down
syndrome?
(A)
0%
(B)
5%
(C)
15%
(D)
100%
90.
Which of the following are examples of
multifactorial disorders?
(A)
Robertsonian translocations
(B)
cystic fibrosis and sickle cell anemia
(C)
heart disease and diabetes
(D)
Duchenne muscular dystrophy and
hemophilia
91.
Assuming that one X chromosome in
each of the following karyotypes has a muta-
tion that causes Duchenne muscular dystro-
phy, which one of the karyotypes is that of an
individual afflicted with this X-linked reces-
sive disease?
(A)
47,XXY
(B)
47,XXX
(C)
46,XX
(D)
47,XYY
92.
Which one of the following suggests that
a disease under consideration is probably
multifactorial?
(A)
The disease occurs more frequently in
females than males.
(B)
The risk of the disease is the same for
both sexes.
(C)
The risk of the disease is 50% for children
of an affected parent.
(D)
The disease occurs in all children of an
affected female.
93.
Marfan syndrome is an autosomal domi-
nant disorder. Jim has no signs of Marfan
syndrome, but his mother and his son are
both affected. This is an example of which of
the following?
(A)
allelic heterogeneity
(B)
variable expressivity
(C)
non-penetrance
(D)
locus heterogeneity
94.
Transcription factors that control spatial
patterning in early human development
belong to what family of genes?
(A)
the abl proto-oncogene family
(B)
the bcr proto-gene family.
(C)
the delta F508 gene family
(D)
the homeotic (HOX) gene family
95.
Which one of the following should be
offered amniocentesis for chromosome
analysis?
(A)
a woman over 35
(B)
a 25-year-old woman who has had one
miscarriage that was 46,XY
(C)
a 25-year-old woman whose husband is 35
(D)
a woman who is a carrier of the
deltaF508 cystic fibrosis deletion
96.
The central dogma of genetics is that a
DNA code is translated into a functional pro-
tein. The correct order of events by which this
is accomplished is which of the following?
(A)
translation, translocation, synthesis
(B)
gene, transcription, translation, protein
(C)
gene, protein, transcription, translation
(D)
gene, protein, translation, transcription
97.
Female carriers of X-linked recessive dis-
eases sometimes exhibit some symptoms of
the disease. This is most likely due to which
one of the following?
(A)
variable expressivity
(B)
mitochondrial inheritance
(C)
Lyonization (inactivation of one of the X
chromosomes in females)
(D)
non-penetrance
98.
In achondroplastic dwarfism, an autoso-
mal dominant disease, the gene is lethal in
the homozygous state. What is the percent of
conceptions from a couple, both of whom
have achondroplastic dwarfism, that will be
homozygous for the gene?
(A)
0%
(B)
25%
(C)
50%
(D)
100%
99.
In a pericentric inversion, which one of
the following changes its position on the
chromosome?
(A)
the centromere
(B)
the mitochondria
(C)
the long arm only
(D)
the short arm only
100.
Sickle cell heterozygotes have some
degree of protection against malaria. Because
of this, the frequency of the “S” allele (the
mutated allele) in sickle cell would be
expected to do which one of the following?
(A)
decrease in the population
(B)
increase in the population
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(C)
not change
(D)
fall to “0”
101.
Because of the risk of strokes, a stat
cytogenetics study is required in suspected
cases of which one of the following?
(A)
chronic myeloid leukemia (CML)
(B)
acute promyelocytic leukemia (PML)
(C)
acute myeloid leukemia (AML) with MLL
translocations
(D)
AML with inversion 16 and eosinophilia
102.
Regarding meiosis, which of the follow-
ing statements applies?
(A)
In females, meiosis is suspended in
prophase I until ovulation.
(B)
In females, two mature ova are produced
in every meiosis.
(C)
At the end of meiosis, there are four
mature ova.
(D)
“Crossing over” does not occur during
oogenesis.
103.
A non-disjunction of chromosome 21
occurs during meiosis I in a woman. The
non-disjoined chromosome 21 homologues
go to the polar body. Which one of the fol-
lowing is the most likely outcome?
(A)
If the ovum is fertilized by a normal
sperm, the conceptus will be trisomic for
chromosome 21.
(B)
If the ovum is fertilized by a normal
sperm, the conceptus will be monosomic
for chromosome 21.
(C)
If the ovum is fertilized by a normal
sperm, there will be no copies of chro-
mosome 21.
(D)
If the ovum is fertilized by a normal
sperm, the conceptus will have a normal
karyotype.
Questions 104 and 105 are based on the follow-
ing family history.
Mr. and Mrs. C have one normal female
child. They have a second male child who has
multiple congenital anomalies. Cytogenetic
studies of the child at birth revealed a deriva-
tive chromosome 11 formed from a translo-
cation between one chromosome 11 and one
chromosome 22. The parents refused cytoge-
netic studies. When Mrs. C became pregnant,
she refused prenatal diagnosis. The full-term
male infant was born with birth defects simi-
lar to his brother’s and was found by cytoge-
netic studies to have the same derivative
chromosome 11. There is no family history of
birth defects on either side.
104.
Which one of the following is the most
likely explanation for this family history?
(A)
One of the parents is a carrier of a bal-
anced reciprocal translocation between
chromosomes 11 and 22.
(B)
Mrs. C carries an X-linked recessive gene.
(C)
Mr. C is the carrier of a Robertsonian
translocation.
(D)
The translocations are a coincidence.
105.
Which one of the following statements
about the above family history is true?
(A)
The derivative chromosome in the broth-
ers came from adjacent segregation of
the balanced reciprocal translocation at
meiosis in the carrier parent.
(B)
The derivative chromosomes in the broth-
ers are the result of two unrelated events.
(C)
The sister probably has the same kary-
otype as her brothers.
(D)
The birth defects in the brothers are
most likely the result of X-linked reces-
sive inheritance.
106.
The genotype of a person for any spe-
cific gene is determined by which one of the
following?
(A)
affinity of the gene for transcription fac-
tor binding motifs
(B)
the number of introns the gene contains
(C)
the presence or absence of short inter-
spersed elements within the gene
(D)
the alleles present at the gene locus
107.
The functional portion of the gene that
codes for proteins is which one of the follow-
ing?
(A)
introns
(B)
exons
(C)
promoter
(D)
enhancer
108.
A pregnant patient with incontinentia
pigmenti (X-linked dominant condition)
comes to you for her obstetrical care and she
gives you the following history: She has had
2 male stillbirths, one early miscarriage (sex
unknown), a daughter who is healthy with no
physical or mental abnormalities, and a
daughter who has seizures, slow learning,
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abnormal skin pigmentation, and cone-
shaped teeth. The patient has amniocentesis,
which demonstrates the fetus is male. When
you counsel the patient, which of the follow-
ing will you discuss with her?
(A)
The risk for the male fetus to be affected
is 100%.
(B)
The risk for her healthy daughter to have
an affected son is 100%.
(C)
The risk for the male fetus to be affected
is 50%.
(D)
X-linked dominant conditions are usu-
ally lethal in females.
109.
Rudy is affected with Gaucher disease,
an autosomal recessive condition. His wife is
not affected but is a carrier. What is the risk
for their daughter to be affected with the
condition?
(A)
0%
(B)
25%
(C)
50%
(D)
75%
Questions 110–112 are based on the following
family history.
Mrs. H and all three of her children, two sons
and a daughter, have been diagnosed with the
same genetic disease. Her daughter’s son and
daughter are both affected. One of her sons has
a son and a daughter and the other son has two
sons and a daughter but none of these children
have the disease. Mr. H does not have the
disease. In taking the family history, Mrs. H tells
you that her mother and her only sibling, a
brother, have the disease as well, but her niece
and nephew do not. She also believes that her
mother’s mother had the disease but she was
not formally diagnosed with it before her death.
Some affected members of the family have
more severe disease than others but all affected
persons show some signs of the disease.
110.
The risk for Mrs. H’s daughter to have
another affected child with this genetic dis-
ease is which of the following?
(A)
0%
(B)
25%
(C)
50%
(D)
100%
111.
The risk for a son of Mrs. H to have an
affected child with this genetic disease is
which of the following?
(A)
0%
(B)
25%
(C)
50%
(D)
100%
112.
The difference in severity of clinical
symptoms among the affected family mem-
bers in this family may be explained by
which of the following?
(A)
variable expressivity
(B)
allelic heterogeneity
(C)
heteroplasmy
(D)
incomplete penetrance
Questions 113 and 114 are based on the follow-
ing family history.
Classical phenylketonuria (PKU) is an impor-
tant inborn error of metabolism caused by a
defect in the enzyme phenylalanine hydroxy-
lase (PAH). PKU causes mental retardation by
disrupting myelin formation and protein syn-
thesis in the brain. PKU can be successfully
treated by dietary therapy. The gene for PAH
maps to chromosome l2q24. Mr. and Mrs. B
have two children with PKU, a son and a
daughter. Mr. and Mrs. B also have a son and
daughter who do not have PKU. No one else
in the family has PKU but Mr. and Mrs. B have
recently learned that they are third cousins.
Mrs. B has a sister who has a daughter and
Mr. B has a brother who has a son. They are of
Swedish ancestry on both sides of the family.
113.
What is the risk that Mr. and Mrs. B
could have another affected child with PKU?
(A)
0%
(B)
25%
(C)
50%
(D)
75%
(E)
100%
114.
What is the risk that Mrs. B’s sister is a
carrier of a PKU mutation?
(A)
0%
(B)
25%
(C)
50%
(D)
75%
(E)
100%
Questions 115 and 116 are based on the follow-
ing family history.
Felicity and Ben have two girls (Angela
and Renee) and are expecting a baby boy.
Both Felicity and her mother Pam have
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neurofibromatosis (NF) type I. Angela and
Renee have not shown any signs of NF-I to
date. Felicity has numerous cafe-au-lait
spots (more than 100), neurofibromas, Lisch
nodules, axillary and inguinal freckling, and
a large plexiform neurofibroma on her back.
Pam has 10 small cafe-au-lait spots, 3 neu-
rofibromas, and axillary freckling.
115.
What is the risk for Felicity’s male child
to have NF-I?
(A)
0%
(B)
25%
(C)
33%
(D)
50%
(E)
100%
116.
The difference in severity of clinical
symptoms between Felicity and her mother
can best be explained by which one of the
following?
(A)
pleiotropy
(B)
incomplete penetrance
(C)
variable expressivity
(D)
anticipation
117.
Hemochromatosis is an autosomal
recessive disease that is relatively common
in the population (1 in 500). The frequency of
the mutated gene is thus 0.045. The disease
can be treated successfully by periodic
removal of blood but failure to recognize it
can lead to a number of serious conditions.
Population screening for carriers is being
considered. What is the expected carrier fre-
quency in the population?
(A)
0.086
(B)
0.100
(C)
0.356
(D)
0.492
(E)
0.706
118.
The species of mosquito that carries the
malaria parasite Plasmodium falciparum is
spreading northward, presumably because
of global warming, and the incidence of
malaria in these regions is on the rise. Which
one of the following is the most likely conse-
quence of this range extension?
(A)
The frequency of the sickle cell gene (S
gene) will decrease in human popula-
tions in these areas.
(B)
The frequency of people homozygous for
the normal allele of the sickle cell gene
(A) will increase.
(C)
Human A and S gene frequencies will not
change.
(D)
The frequency of heterozygotes (AS) in
the human population will increase.
119.
The gene frequency “p” for the autoso-
mal dominant disease, Marfan syndrome, is
0.00005. What is the frequency of “q”?
(A)
0.000707
(B)
0.00025
(C)
0.00025
(D)
0.99995
120.
The Philadelphia chromosome is pro-
duced by which one of the following?
(A)
A balanced reciprocal translocation
between chromosomes 9 and 22.
(B)
A balanced reciprocal translocation
between chromosomes 8 and 21.
(C)
A fusion of the p53 and abl proto-
oncogenes.
(D)
Loss of heterozygosity.
121.
In almost every tumor examined, the
telomerase gene has been reactivated. This
observation may explain which of the follow-
ing?
(A)
how telomeres assist in DNA synthesis
(B)
how tumor cells metastasize
(C)
how tumor cells become “immortal”
(D)
why telomeres are translocated in all
cancers
122.
Which one of the following chromo-
somes is never involved in a Robertsonian
translocation?
(A)
13
(B)
18
(C)
21
(D)
22
123.
At the end of meiosis I, how many
chromosomes are present in the daughter
cells?
(A)
23
(B)
46
(C)
69
(D)
92
124.
A non-disjunction of an X chromosome
occurs in a 46,XX conceptus during the
first cell division resulting in mosaicism.
Providing the embryo goes to term, what cell
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