USMLE Genetics Exam Questions
with All Correct Answers
What is linkage disequalibrium? - Answer-Tendency for certain alleles at 2 linked loci to
occur together more often than expected by chance...Varies between populations.
What is a dominant negative mutation? - Answer-When a mutation exerts a dominant
effect, as in a heterozygote produces a nonfuntional altered protein that also prevents
normal gene expression
What is the chromosomal defect in Williams Syndrome? - Answer-Deletion of the long
arm, q arm of chromosome 7, which includes the elastin gene.
What are the clinical manifestations of Williams Syndrome? - Answer-Elfin faces
Well developed verbal skills
Cheerful disposition and friendliness with strangers
MR
CV problems
What is the defect in DiGeorges Syndrome and what are the complications? - Answer-
22q11 deletion-- CATCH 22!
Cardiac abnormalities
Abnormal Facies
Thymic aplasia
Cleft palate
Hypocalcemia
What is Velocardiofacial syndrome? - Answer-A 22q11 microdeletion syndrome with
palate, facial and cardiac defects.
What Triplet repeat is seen in Huntingtons? - Answer-CAG on Ch 4
What triplet repeat is seen in MyoTonic dystrophy? - Answer-CTG
What triplet repeat is seen in FraGile X syndrome? - Answer-CGG
What Triplet repeat is seen in Friedrichs Ataxia? - Answer-CAA
What does ultrasound show in a Down syndrome fetus? - Answer-Increased nuchal
translucency
, What are the results of a pregnancy quad screen on a Down syndrome fetus? - Answer-
Increased B-hCH
Increased Inhibit A
Decreased AFP
Decreased Estriol
What is the most common cause of congenital mental retardation? - Answer-Down
Syndrome
What are the common findings in a Down syndrome Baby? - Answer-MR
Flat facies with epicanthal folds
Simean Crease
Gap between 1st two toes
Duodenal atresia*
Heart disease, usually ASD septum primum
What diseases are Down syndrome babies at increased risk of acquiring? - Answer-
Alzheimers and ALL
What is the most common trisomy after 21? - Answer-18, Edwards syndrome. 18=
Election age
What are the findings of Edwards Syndrome ? - Answer-Micrognathia (small jaw)
Clenched hands
Rocker Bottom Feet
Low set ears
What are the clinical findings of Patau Syndrome? - Answer-PolyDactyly
HoloProsencephaly
Cleft lip or Palate
Microcephaly and micropthalmia
What are the general features of a proto-oncogene WRT causing cancer? - Answer-The
PROTO oncogene is usually related to causing cell growth.
A mutation in this gene leads to an oncogene, which is typically a GAIN IN FUNCTION
of the proliferation gene
Only ONE hit is necessary to mutate a protooncogene
What are the general features of a Tumor Suppressor gene WRT causing cancer? -
Answer-Normal version of the gene is normally responsible for slowing down cell
growth, ie p53.
Mutation in this gene usually leads to a LOSS OF FUNCTION
Two hits on the gene are necessary to mutate is enuf to cause cancer
with All Correct Answers
What is linkage disequalibrium? - Answer-Tendency for certain alleles at 2 linked loci to
occur together more often than expected by chance...Varies between populations.
What is a dominant negative mutation? - Answer-When a mutation exerts a dominant
effect, as in a heterozygote produces a nonfuntional altered protein that also prevents
normal gene expression
What is the chromosomal defect in Williams Syndrome? - Answer-Deletion of the long
arm, q arm of chromosome 7, which includes the elastin gene.
What are the clinical manifestations of Williams Syndrome? - Answer-Elfin faces
Well developed verbal skills
Cheerful disposition and friendliness with strangers
MR
CV problems
What is the defect in DiGeorges Syndrome and what are the complications? - Answer-
22q11 deletion-- CATCH 22!
Cardiac abnormalities
Abnormal Facies
Thymic aplasia
Cleft palate
Hypocalcemia
What is Velocardiofacial syndrome? - Answer-A 22q11 microdeletion syndrome with
palate, facial and cardiac defects.
What Triplet repeat is seen in Huntingtons? - Answer-CAG on Ch 4
What triplet repeat is seen in MyoTonic dystrophy? - Answer-CTG
What triplet repeat is seen in FraGile X syndrome? - Answer-CGG
What Triplet repeat is seen in Friedrichs Ataxia? - Answer-CAA
What does ultrasound show in a Down syndrome fetus? - Answer-Increased nuchal
translucency
, What are the results of a pregnancy quad screen on a Down syndrome fetus? - Answer-
Increased B-hCH
Increased Inhibit A
Decreased AFP
Decreased Estriol
What is the most common cause of congenital mental retardation? - Answer-Down
Syndrome
What are the common findings in a Down syndrome Baby? - Answer-MR
Flat facies with epicanthal folds
Simean Crease
Gap between 1st two toes
Duodenal atresia*
Heart disease, usually ASD septum primum
What diseases are Down syndrome babies at increased risk of acquiring? - Answer-
Alzheimers and ALL
What is the most common trisomy after 21? - Answer-18, Edwards syndrome. 18=
Election age
What are the findings of Edwards Syndrome ? - Answer-Micrognathia (small jaw)
Clenched hands
Rocker Bottom Feet
Low set ears
What are the clinical findings of Patau Syndrome? - Answer-PolyDactyly
HoloProsencephaly
Cleft lip or Palate
Microcephaly and micropthalmia
What are the general features of a proto-oncogene WRT causing cancer? - Answer-The
PROTO oncogene is usually related to causing cell growth.
A mutation in this gene leads to an oncogene, which is typically a GAIN IN FUNCTION
of the proliferation gene
Only ONE hit is necessary to mutate a protooncogene
What are the general features of a Tumor Suppressor gene WRT causing cancer? -
Answer-Normal version of the gene is normally responsible for slowing down cell
growth, ie p53.
Mutation in this gene usually leads to a LOSS OF FUNCTION
Two hits on the gene are necessary to mutate is enuf to cause cancer
