Question 1

In addition to the lungs,what other major organ is affected by cystic fibrosis?&#10;A) Heart&#10;B) Muscle&#10;C) Brain&#10;D) Pancreas&#10;E) Kidney

Accepted Answer

Cystic fibrosis primarily affects the lungs, but it also affects the pancreas which produces digestive enzymes. In individuals with cystic fibrosis, these enzymes become thick and sticky, leading to blockages in the pancreas and difficulty digesting food. This can cause malnutrition, poor growth, and other digestive problems.

Question 2

Which of the following mutations is associated with the myotonic dystrophy phenotype?&#10;A) A CCTG expansion 3' of ZNF9&#10;B) A deletion in DMPK&#10;C) A trinucleotide repeat expansion 3' of DMPK&#10;D) A and C&#10;E) B and C

Accepted Answer

Myotonic dystrophy is caused by two different mutations, one of them being a trinucleotide repeat expansion 3' of DMPK (Choice C), and the other being a CCTG expansion 3' of ZNF9 (Choice A). Therefore, both choices A and C are correct. Choice B, a deletion in DMPK, is not associated with the myotonic dystrophy phenotype.

Question 3

Which of the following is a feature of the inheritance pattern of Huntington's disease?&#10;A) It is sex-limited&#10;B) The phenotype is not seen until after 50 years of age&#10;C) It exhibits anticipation&#10;D) It is passed only through females&#10;E) All of the above

Accepted Answer

Huntington's disease exhibits anticipation, which means that the severity of the disease increases or the age of onset decreases with each succeeding generation due to an increase in the number of repeats of a specific DNA sequence.

Question 4

Which of the following is potentially the most severe aspect of Marfan syndrome?&#10;A) Blindness&#10;B) Sprains due to joint laxity&#10;C) Dilatation of the ascending aorta&#10;D) Mental retardation&#10;E) Low blood pressure due to excessive height

Accepted Answer

Dilatation of the ascending aorta is potentially the most severe aspect of Marfan syndrome as it can lead to aortic dissection or rupture, which can be life-threatening. Blindness, sprains due to joint laxity, mental retardation, and low blood pressure due to excessive height are all possible symptoms of Marfan syndrome but are not typically as severe as aortic complications.

Question 5

Although deletions in the dystrophin gene cause both Duchenne and Becker muscular dystrophy,what feature is shared by the Becker MD-associated mutations?&#10;A) They maintain the reading frame&#10;B) They are smaller&#10;C) They occur in the 5' region of the gene&#10;D) They occur in the 3' region of the gene&#10;E) They delete an alternate exon

Accepted Answer

Mutations in the dystrophin gene that cause Becker muscular dystrophy maintain the reading frame, meaning that the final protein produced is still functional albeit weakened, while mutations that cause Duchenne muscular dystrophy result in a frameshift and a non-functional protein. The other options are not necessarily true for all Becker MD-associated mutations.

Question 6

Which of the following is true of CFTR mutations?&#10;A) Mutations affecting the function of CFTR are always associated with a classic CF phenotype&#10;B) There are clear genotype-phenotype correlations for CFTR mutations&#10;C) Mutations can present as congenital bilateral absence of the vas deferens as the sole phenotype&#10;D) The IVS8 9T variant allele causes classic CF&#10;E) Pancreatic insufficiency is rarely found in people with the DF508 mutation

Accepted Answer

CFTR mutations can present with a variety of clinical manifestations, and some mutations may only result in congenital bilateral absence of the vas deferens (CBAVD) without classical cystic fibrosis (CF) symptoms.

Answer: B
 Although there are many possible CFTR mutations, there are some genotype-phenotype correlations, meaning that certain mutations are more likely to result in particular symptoms or clinical presentations.

Answer: D
 The IVS8 9T variant allele is not sufficient to cause classic CF on its own, but it may contribute to pathogenicity in combination with other mutations.

Therefore, the correct answer is C and B.

Question 7

Neurofibromin downregulates the activity of which protein?&#10;A) p53&#10;B) RAS&#10;C) RB&#10;D) HNF1A&#10;E) CAPN10

Accepted Answer

Neurofibromin is a negative regulator of RAS, meaning it downregulates its activity. This is why individuals with Neurofibromatosis type 1 have increased RAS activity and an increased risk for tumors.

Question 8

Although anticipation has now been demonstrated for myotonic dystrophy,it was once argued that the appearance of increased severity in successive generations might have been due to which of the following?

A) Sex limitation of the phenotype
B) Ascertainment bias
C) Increased anxiety in the family
D) A negative effect of therapies

Accepted Answer

Ascertainment bias refers to the bias that can occur when a sample is not representative of the population being studied, which can lead to false observations. In this case, the appearance of increased severity in successive generations may have been due to a bias in the selection of affected individuals for study, rather than a true increase in severity.

Question 9

Caf&#233;-au-lait spots are a feature of what phenotype?&#10;A) Charcot-Marie-Tooth disease&#10;B) Myotonic dystrophy&#10;C) Neurofibromatosis&#10;D) Huntington disease&#10;E) Marfan syndrome

Accepted Answer

Café-au-lait spots are a feature of neurofibromatosis.

Question 10

The reciprocal deletion of the duplication causing hereditary and motor-sensory neuropathy is associated with what phenotype?&#10;A) Normal phenotype&#10;B) Recurrent miscarriages&#10;C) Charcot-Marie-Tooth disease&#10;D) Pain insensitivity&#10;E) Hereditary neuropathy with pressure palsies

Accepted Answer

The reciprocal deletion of the duplication causing Charcot-Marie-Tooth disease type 1A results in hereditary neuropathy with pressure palsies (HNPP).

Deck 19: Single-Gene Disorders