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Neurosensory and Neuromuscular System - Neurology, Ophthalmology, Otolaryngology Part 1 (20 test)
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1. A newborn Caucasian girl exhibits extreme hypotonia (low muscle tone) after an unremarkable pregnancy and delivery. The hypotonia is so severe that tube- feeding is required, and the physician notes facial changes (almond-shaped eyes, down-turned corners of the mouth) and underdevelopment of the labia that suggest a diagnosis of Prader-Willi syndrome (MIM*176270). It can involve changes in gene structure or modification. The physician orders chromosome testing to look for the characteristic chromosome 15 deletion in Prader-Willi syndrome and DNA testing to evaluate an alteration of genomic Which of the following processes occurs at the fifth position of cytidine and often correlates with gene inactivation?
- Gene conversion
- Sister chromatid exchange
- Gene rearrangement
- DNA methylation
2. A 13-year-old African American adolescent notices decreased performance in basketball and drooping of his eyelids when tired. He complains to his pediatrician that his leg muscles seem smaller despite consistent weight training, and he has trouble keeping his balance with his eyes closed or when not concentrating. The physician suspects Kearns-Sayre syndrome (MIM*530000), and confirms the diagnosis by demonstrating a deletion of mitochondrial DNA in tissue obtained by muscle Unique properties of mitochondrial DNA are best summarized as which of the following?
- Circular, single-stranded, comprising 1% of cellular DNA with high mutation rates
- Linear duplex DNA with a length similar to that of one nuclear chromosome, present as 50 to 100 copies per cell
- Circular duplex DNA of about 16,000 bp that encodes unique tRNAs and several mitochondrial proteins
- Circular, single-stranded DNA with low mutation rate that encodes a minority of mitochondrial peptides
- Linear duplex DNA that encodes over 70 proteins of the respiratory chain and has a mutation rate 5 to 10 times higher than nuclear DNA
3. Disorders with abnormalities of the respiratory chain present with central nervous system and muscle symptoms (seizures, low tone) due to energy A preliminary test to decide if a patient may have a mitochondrial electron transport disorders examines the ratio of pyruvate to that of its product under resting conditions. What is the ratio and how would it be affected by abnormal electron transport?
4. A 24-year-old Caucasian female of Swedish origin requests evaluation for frequent early fatigue, heart palpitations, and muscle cramping during Her symptoms have been present since childhood but have become more aggravating since she has taken up jogging for exercise. Blood testing during exercise demonstrates a rapid increase in succinate, alanine, lactate, and pyruvate. Her physician suspects an inherited enzyme deficiency that interferes with oxidative-phosphorylation in muscle. Which of the following pathways, enzyme reaction, and associated product levels are most likely deficient?
- Glycolysis, pyruvate kinase, and coenzyme A
- Glycolysis, hexokinase, and glucose 1-phosphate
- Gluconeogenesis, pyruvate carboxylase, and carbon dioxide
- Gluconeogenesis, pyruvate carboxylase, and ATP
- Citric acid cycle, fumarase, and succinyl-CoA
- Citric acid cycle, succinate dehydrogenase, and FADH2
5. A 55-year-old Caucasian male exhibits progressive neurologic symptoms of deteriorating handwriting, declining sports performance, and increased clumsiness that has caused accidents in his construction work. Hospital studies reveal he has increased muscle fatigue accompanied by rising lactic acid and decreased Which of the following compounds would be the best candidate for therapy if successfully delivered to muscle?
6. An 8-year-old Caucasian boy presents with ataxia (poor muscle coordination with abnormal gait) and anemia, which are suggestive of a mitochondrial disorder called Pearson syndrome (MIM*557000). This disorder is caused by a large mitochondrial DNA deletion, rendering multiple mitochondrial pathways Which of the following conversions would be most affected in this child?
- Glucose to glucose 6-phosphate
- UDP-glucose to glycogen
- D-glucuronate to L-gulonate to ascorbate
- Oxaloacetate to citrate
- D-glyceraldehyde to glyceraldehyde 3-phosphate
7. A 13-year-old Hispanic adolescent presents to clinic complaining of muscle cramps on Past history indicates he had some coordination problems in childhood and received occupational therapy. Blood tests show an increased amount of lactic acid at rest, with dramatic increases on exercise testing. Simultaneous measures by a surface pulse-oxygenation probe showed capillary oxygen saturation of 97% at rest and 96% with exercise (normal >95%). The abnormality most likely involves which of the following?
- Glycolysis in the lysosomes
- Glycolysis in the cytosol
- Respiratory chain in the mitochondria
- Glycogen breakdown in the mitochondria
- Glycogen synthesis in the cytosol
8. A 12-hour-old Caucasian boy is noted to maintain a frog-leg position with a weak cry and minimal spontaneous movement. A muscular dystrophy is suspected, and a serum enzyme is measured that reflects the abundance of a high-energy storage molecule in Which of the following enzymes was measured?
- Adenosine triphosphatase
- Creatine phosphokinase
- Glucose-1-phosphate dehydrogenase
- ATP synthase
9. Nerve stimulation of skeletal muscle causes the release of calcium from sarcoplasmic reticulum and leads to muscle Simultaneously, the increased calcium concentration causes which of the following responses?
- A dramatic rise in cyclic AMP levels
- Inactivation of glycogen phosphorylase
- Activation of phosphorylase kinase
- Activation of cyclic AMP phosphodiesterase
- Activation of protein phosphatase
10. A 16-year-old Caucasian adolescent presents for neurology evaluation because of fatigue that prevents participation in gym class. A consulting neurologist finds muscle weakness in the girl’s arms and Laboratory testing demonstrates elevated serum triacylglycerides and borderline low glucose. Muscle biopsy shows increased numbers of lipid vacuoles. Which of the following is the most likely diagnosis?
- Fatty acid synthase deficiency
- Tay-Sachs disease
- Carnitine deficiency
- Biotin deficiency
- Lipoprotein lipase deficiency
11. A 23-year-old Caucasian female consults her physician because of occasional periods of confusion and lethargy, usually after a The physician suspects a deficiency in an enzyme of the urea cycle, which in this case would most likely be which of the following?
- Argininosuccinic acid synthase
- Carbamoyl phosphate synthase I
- Ornithine transcarbamylase
12. Which of the following disorders or symptoms are typical of cobalamin deficiency?
- Pernicious anemia
13. Which of the following foods should be emphasized for individuals with dry eyes and decreased vision in dim light?
- Human and cow (not goat) milk, uncooked fruits, and vegetables
- Milk, eggs, meats, and fruits
- Vegetables, cereals, and fruits
- Liver, poultry, and eggs
- Egg yolks, fish oils, and leafy vegetables
14. A 5-year-old African American girl complains that she is always tired and refuses to play with her friends. Evaluation reveals that she has mild elevations of lactic acid, and mitochondrial DNA studies reveal a mutation in the mitochondrial gamma polymerase (POLG-MIM*174763). POLG deficiencies lead to depletion of DNA in a proportion of the patient’s mitochondria with less efficient oxidative Which of the following compounds would be most effective in improving the girl’s energy metabolism?
- Glucose 6-phosphate, xylitol
- Glucose 1-phosphate, UDP-glucose
- Ornithine, arginine
- Lipoic acid, thiamine
- Creatine, lactate
15. Your patient is an adult who avoids bright light; has sore eyes, mouth, and tongue; plus feels tired and confused. Which of the following vitamins would most likely be deficient in this patient?
16. A 22-year-old African American female presents with a complaint of muscle weakness following Neurological examination reveals that the muscles supplied by cranial nerves are most affected. You suspect myasthenia gravis, a diagnosis confirmed by antibodies against which of the following in the patient’s blood?
- Muscle mitochondrial membranes
- Cranial nerve synaptic membranes
- Cranial nerve presynaptic membranes
- Acetylcholine receptors
17. A 35-year-old Caucasian female develops aching and numbness in her legs at night, which she at first ascribes to fatigue from She then experiences the same symptoms in her arms. Her physician suspects amyotrophic lateral sclerosis (ALS, Lou Gehrig disease) and the female, who was adopted, seeks information on her biological parents. She locates her biological mother, who tells her that her father died from a neurologic disease in his thirties, leaving her destitute and forcing her to place the new baby for adoption. ALS usually occurs as an isolated case with onset at older ages but occasionally presents in younger people, following an autosomal dominant inheritance pattern. There is a slight predominance of males. Which of the following best summarizes this information?
- ALS is a genetic
- ALS is an autosomal dominant disease with occasional new
- ALS is a sporadic
- ALS is a congenital
- ALS exhibits multifactorial determination with occasional dominant
18. Assume that D and d alleles derive from a single locus and that the presence of one D allele causes deafness. Match the mating of a genotype Dd father with a genotype dd mother and their probabilities for genotypes in
- 1 DD
- ½ Dd, ½ dd
- ¼ DD, ½ Dd, and ¼ dd
- ½ DD, ½ Dd
- 1 dd
19. Huntington disease (MIM*143100) is an autosomal dominant, progressive neurodegenerative disease that causes uncontrolled physical movements and mental deterioration with usual onset in middle A husband and wife have three children, two boys and one girl. The husband was diagnosed with Huntington disease in his mid-fifties, as was his father. The wife has no symptoms and no family history of Huntington disease. Assuming 100% penetrance, what is the probability that all three of his children will eventually develop Huntington disease?
- Virtually 0
20. A 51-year-old Hispanic male presents to the physician’s office to ask questions about color The patient is color-blind, as is one of his brothers. His maternal grandfather was color-blind, but his mother, father, daughter, and another brother are not. His daughter is now pregnant. What is the risk that her child will be color-blind?
- Virtually 0