2001a-Paper 1 – Medical Sciences

Question 1

A 47-year-old woman with overt thyrotoxicosis is found to have aortic stenosis.
Which one of the following features, if present in this woman, is most likely to indicate the need for aortic valve replacement?

Accepted Answer

D. An aortic valve orifice area of 0.9 cm2.

Answer

A. A peak systolic left ventricular aortic pressure gradient of 60 mmHg.

Answer

B. The presence of New York Heart Association (NYHA) class III angina.

Answer

C. A resting heart rate greater than 120/minute.

Answer

E. The presence of concomitant moderate aortic regurgitation

Question 2

The diagram below shows cumulative quantal dose-response curves for a hypothetical drug (drug X). The Y-axis represents the percentage of the population studied who: for curve (a) achieved the desired therapeutic effect at a given dose; and for curve (b) experienced the most important toxic effect at a given dose.
Based on this information, the best estimate of the therapeutic index of drug X is approximately:

Accepted Answer

E. 3.

Answer

A. 0.

Answer

B. 0.3.

Answer

C. 0.7.

Answer

D. 1.

Question 3

The alveolar-arterial gradient for oxygen tension in arterial blood (PA-aO2) can be up to 15 mmHg in healthy young adults and as high as 30 mmHg in elderly people.
Which one of the following is considered to be the predominant physiological mechanism for a normal PA-aO2?

Accepted Answer

D. Ventilation/perfusion (V/Q) inequality.

Answer

A. Variation in distribution of ventilation.

Answer

B. Variation in diffusion for oxygen.

Answer

C. Right to left shunt.

Answer

E. Variation in distribution of pulmonary blood flow.

Question 4

Significant intercurrent illness is commonly associated with disturbances of thyroid function (sick euthyroid syndrome).
Which one of the following is least likely to be present in a euthyroid patient with a severe illness?

Accepted Answer

B. Raised free triiodothyronine (free T3).

Answer

A. Raised free thyroxine (free T4).

Answer

C. Low free T3.

Answer

D. Low thyroid-stimulating hormone (TSH).

Answer

E. Raised TSH.

Question 5

At 72 hours following a significant paracetamol overdose, which one of the following tests will allow the best prediction of death or need for liver transplantation?

Accepted Answer

C. Prothrombin time-international normalised ratio (PT-INR).

Answer

A. Serum alanine transaminase (ALT).

Answer

B. Serum bilirubin.

Answer

D. Serum gamma glutamyltranspeptidase (GGT).

Answer

E. Blood ammonia.

Question 6

The most common cause of blindness in elderly Caucasians is:

Accepted Answer

C. macular degeneration.

Answer

A. glaucoma.

Answer

B. cataract.

Answer

D. diabetes mellitus.

Answer

E. retinal ischaemia.

Question 7

Graft-versus-host disease is a major complication of allogeneic stem cell transplantation for haematological malignancy in adults.
Which one of the following has the least influence on the risk of developing graft-versus-host disease?

Accepted Answer

B. Donor-recipient ABO blood group incompatibility.

Answer

A. Age of recipient.

Answer

C. In vitro T cell depletion of the graft.

Answer

D. Type of HLA-matched donor (sibling versus unrelated).

Answer

E. Donor-recipient HLA mismatch.

Question 8

Dendritic cells are distinguished by an exceptional ability to carry out which one of the following immune functions?

Accepted Answer

E. Antigen presentation

Answer

A. Phagocytosis.

Answer

B. Cytokine secretion.

Answer

C. Chemokine secretion.

Answer

D. Immunoglobulin secretion.

Question 9

The most useful investigation for the diagnosis of multiple sclerosis is:

Accepted Answer

C. magnetic resonance imaging (MRI) scan of the brain.

Answer

A. cerebrospinal fluid protein concentration.

Answer

B. visual evoked responses.

Answer

D. serum oligoclonal bands.

Answer

E. cerebrospinal fluid microscopy

Question 10

A mutation is located in the middle portion of a double-stranded DNA molecule 200 nucleotides long. At each end of the DNA molecule are sites at which short DNA primers for the polymerase chain reaction (PCR) bind to each strand.
In the figures shown below, five possible combinations of primer location and orientation relative to the mutation are shown. In each figure, the long pair of arrows represents the anti-parallel strands of the long DNA molecule and the short arrows represent each short single-stranded DNA primer binding to the closer of the two long strands. The mutation is located at position (II), the primers are located at positions (I) and (III), and the arrowhead on each DNA strand indicates the direction of DNA polymerisation (5’ to 3’).
Which one of the following combinations of primer location and orientation is required to amplify the mutation by PCR?

Question 11

A number of patients in a ward have been found to be colonised with vancomycin-resistant enterococci. What would be the best laboratory test to determine if transmission from one patient to another has occurred?

Accepted Answer

D. Pulse-field gel electrophoresis.

Answer

A. Comparison of antibiotic susceptibility (antibiogram).

Answer

B. Polymerase chain reaction (PCR) for the van A and van B genes.

Answer

C. Enterococcal serology.

Answer

E. Speciation (e.g. faecalis vs. faecium).

Question 12

A 35-year-old woman with hypertrophic cardiomyopathy presents with chest pain and palpitations. Her heart rate is 155/minute and irregular, and her blood pressure is 130/80 mmHg.
What is the most appropriate initial therapy?

Accepted Answer

A. Beta-adrenergic blocker.

Answer

B. Nitroglycerine.

Answer

C. Amiodarone.

Answer

D. Frusemide.

Answer

E. Digoxin.

Question 13

In a patient with cryptogenic fibrosing alveolitis (idiopathic pulmonary fibrosis), the finding on bronchoalveolar lavage of an elevated proportion of which one of the following cell types is associated with a better response to therapy?

Accepted Answer

B. Lymphocytes.

Answer

A. Eosinophils.

Answer

C. Macrophages.

Answer

D. Mast cells.

Answer

E. Neutrophils.

Question 14

A bioavailability study has been performed to compare a proposed new generic capsule, in a strength of 50 mg, with a marketed tablet preparation in a strength of 100 mg. The active ingredient is a drug with linear kinetics. A cross-over design was used, with each subject receiving, in random order and with an adequate wash-out period, a single oral dose of one tablet on one occasion and one capsule on the other. The mean results for the area under the plasma concentration versus time curve (AUC) are 300 mg.h/L for the capsule, and 500 mg.h/L for the tablet.
The best estimate of the relative bioavailability of the capsule with respect to the tablet is:

Accepted Answer

C. 1.2.

Answer

A. 0.3.

Answer

B. 0.6.

Answer

D. 1.7.

Answer

E. 3.3.

Question 15

A 25-year-old woman presents to the emergency department with renal colic and macroscopic haematuria. She reports having had several previous episodes treated at another hospital.
The least likely diagnosis is:

Accepted Answer

D. Goodpasture’s syndrome.

Answer

A. IgA disease.

Answer

B. warfarin use.

Answer

C. narcotic abuse.

Answer

E. polycystic kidney disease.

Question 16

The COX-2 isoform of cyclo-oxygenase is most strongly expressed in which one of the following tissues?

Accepted Answer

E. Rheumatoid synovium.

Answer

A. Platelets.

Answer

B. Established scar tissue.

Answer

C. Synovium from osteoarthritic joint.

Answer

D. Gastric mucosa.

Question 17

Which one of the following is the most potent inhibitor of aldosterone secretion in a healthy individual?

Accepted Answer

C. Elevated plasma atrial natriuretic peptide.

Answer

A. Elevated plasma potassium.

Answer

B. Elevated plasma angiotensin II.

Answer

D. Elevated adrenocorticotrophic hormone.

Answer

E. Dietary sodium restriction.

Question 18

A 45-year-old man develops stage C cancer of the caecum. There is a strong family history of bowel cancer in the absence of polyps and there is no history of colitis.
The most likely underlying inherited genetic abnormality is in:

Accepted Answer

B. the DNA mismatch repair (MMR) gene.

Answer

A. the ras gene.

Answer

C. the p-glycoprotein (MDR1) gene.

Answer

D. the adenomatous polyposis coli (APC) gene.

Answer

E. the deleted in colon cancer (DCC) gene.

Question 19

A 19-year-old woman presents with recent-onset of right leg swelling and pleuritic chest pain and is found to have iliofemoral thrombosis on Doppler ultrasound examination. Results of a ventilation-perfusion lung scan indicate a high probability for pulmonary emboli. She had been taking the oral contraceptive pill for the last three years but has now ceased. She is a non-smoker. There is no significant medical history and no known family history of venous thromboembolism.
Which one of the following investigations for an underlying hypercoagulable state is most likely to be affected by the presence of the extensive thrombosis?

Accepted Answer

B. Antithrombin level.

Answer

A. Antiphospholipid antibody screen.

Answer

C. Factor V and prothrombin genotype assessment.

Answer

D. Activated partial thromboplastin time (APTT).

Answer

E. Full blood count including blood film.

Question 20

Which one of the following is associated with the highest risk of NSAID (non-steroidal anti-inflammatory drug)-induced gastric ulceration?

Accepted Answer

D. Advanced age.

Answer

A. Concomitant use of steroids.

Answer

B. Infection with Helicobacter pylori.

Answer

C. Higher therapeutic dose of NSAID.

Answer

E. Concomitant use of anticoagulants.

Question 21

T lymphocytes expressing both CD4 and CD8 on the cell surface are most likely to be found in which one of the following anatomical locations in healthy individuals?

Accepted Answer

B. Thymus.

Answer

A. Bone marrow.

Answer

C. Peripheral blood.

Answer

D. Lymph nodes.

Answer

E. Spleen.

Question 22

In treating constipation, which one of the following agents administered over an extended period of time is most likely to lose its effectiveness?

Accepted Answer

C. Senna.

Answer

A. Docusate sodium (Coloxyl).

Answer

B. Lactulose.

Answer

D. Psyllium husk powder (Metamucil).

Answer

E. Epsom salts.

Question 23

An 18-year-old woman presents with a two-week history of cervical lymphadenopathy, fever, fatigue and myalgia. A Paul-Bunnell test (heterophile antibody) has been negative on two occasions, a week apart. Full blood examination reveals a lymphocytosis with many atypical lymphocytes.
The most likely diagnosis is acute:

Accepted Answer

D. cytomegalovirus (CMV) infection.

Answer

A. Epstein-Barr virus (EBV) infection.

Answer

B. streptococcal pharyngitis.

Answer

C. toxoplasmosis.

Answer

E. human immunodeficiency virus (HIV) infection.

Question 24

The picture below shows a computed tomography (CT) scan of the heart.
Which one of the following is the most likely diagnosis?

Accepted Answer

B. Left atrial myxoma.

Answer

A. Metastatic tumour in the pericardium.

Answer

C. Ruptured myocardial papilla.

Answer

D. Cor triatriatum.

Answer

E. St. Jude mitral valve prosthesis.

Question 25

Vertigo which occurs with neck extension is most likely due to:

Accepted Answer

B. benign paroxysmal positional vertigo.

Answer

A. cervical spondylosis.

Answer

C. kinking of the vertebral artery.

Answer

D. endolymphatic hydrops.

Answer

E. Chiari 1 malformation.

Question 26

Allopurinol precipitates azathioprine toxicity by which one of the following mechanisms?

Accepted Answer

D. Prolongation of the half-life of the biologically active azathioprine metabolite.

Answer

A. Displacement of azathioprine from protein-binding sites.

Answer

B. Impairment of the renal excretion of azathioprine.

Answer

C. Promotion of gastrointestinal absorption of azathioprine.

Answer

E. Inhibition of hydrolysis of azathioprine.

Question 27

Which one of the following mutations in a gene is most likely to disrupt the production of a protein?

Accepted Answer

D. Nonsense change.

Answer

A. Splicing defect.

Answer

B. Missense change.

Answer

C. Nucleotide transversion.

Answer

E. A three base pair deletion.

Question 28

In a patient with a severe exacerbation of asthma, the use of a peak-flow meter may underestimate the severity of airflow limitation compared to the use of spirometry and measurement of the forced expiratory volume in 1 second (FEV1).
Which one of the following is mainly responsible for this reduction in the accuracy of the peak-flow meter?

Accepted Answer

C. The effort-dependent component of the forced expiratory manoeuvre.

Answer

A. The hyperinflation of severe asthma.

Answer

B. The effort-independent component of the forced expiratory manoeuvre.

Answer

D. Narrowing of small airways.

Answer

E. Narrowing of large airways.

Question 29

The most important rationale for using adjuvant chemotherapy soon after surgery for cancer (rather than deferring chemotherapy until the cancer has recurred) is that after surgery:

Accepted Answer

A. cancer volume is smaller.

Answer

B. there is no resistance to cytotoxic agents.

Answer

C. there are fewer cells in cell cycle.

Answer

D. drug penetration into the tissues is reduced.

Answer

E. cancer growth is slower.

Question 30

Which one of the following is the best predictor of outcome in a patient with colorectal cancer?

Accepted Answer

A. Tumour stage.

Answer

B. Degree of microsatellite instability.

Answer

C. Ethnic background.

Answer

D. Strong family history.

Answer

E. Sporadic occurrence.

Question 31

A 32-year-old woman, who has recently migrated from India, is breastfeeding her third child and presents with lethargy and a history of recurrent chest infection. She has a vegetarian diet. Physical examination shows her to be anaemic with no site of blood loss clinically evident and no other abnormalities.
Investigations show:
Full blood count
haemoglobin 64 g/L [120-155]
mean corpuscular volume (MCV) 68 fL [80-95]
white cell count 7.4 x 109/L [3.5-9.5]
differential normal
platelet count 412 x 109/L [130-330]
Blood film is shown below.
With respect to the patient’s anaemia, which one of the following laboratory results has the most diagnostic value?

Accepted Answer

B. A lower than normal serum ferritin level.

Answer

A. A lower than normal serum iron level.

Answer

C. A higher than normal serum transferrin level.

Answer

D. A negative urinary haemosiderin test.

Answer

E. A normal plasma haemoglobin A2 leve

Question 32

A 28-year-old woman presents with galactorrhoea. She has been treated for hypothyroidism for five years with thyroxine 0.1 mg/day. She is also receiving lithium carbonate for depression and her serum lithium levels are in the mid-therapeutic range. She takes diazepam 5 mg nocte for insomnia and metoclopramide 10 mg as required for nausea. Her serum prolactin concentration is 1800 mU/L [<600].
From this history, which one of the following factors is most likely to be responsible for her hyperprolactinaemia and galactorrhoea?

Accepted Answer

A. Use of metoclopramide.

Answer

B. History of hypothyroidism.

Answer

C. Treatment with thyroxine.

Answer

D. Use of lithium.

Answer

E. Use of diazepam.

Question 33

In renal transplant biopsies, which one of the following features of acute rejection has the worst prognostic implication?

Accepted Answer

D. Vascular injury.

Answer

A. Glomerular T cell infiltrate.

Answer

B. Dense interstitial mononuclear infiltrate.

Answer

C. Increased expression of HLA-DR on graft cells.

Answer

E. Tubulitis due to CD8+ T cells.

Question 34

Which one of the following biologically active components of the complement cascade is most directly responsible for the formation of transmembrane channels leading to cell lysis?

Accepted Answer

E. C5-9.

Answer

A. C3a.

Answer

B. C3b.

Answer

C. C4a.

Answer

D. C5a.

Question 35

Which one of the following is the most common association of the abnormality shown in the X-ray above?

Accepted Answer

C. Old age.

Answer

A. Haemochromatosis.

Answer

B. Hypomagnesaemia.

Answer

D. Hyperparathyroidism.

Answer

E. Osteoporosis.

Question 36

A young man presents with breathlessness and ankle swelling. He had a ventricular septal defect (VSD) repaired at the age of three years. He is centrally cyanosed and has a prominent right ventricular heave on palpation of the chest.
The most likely finding is:

Accepted Answer

A. pulmonary hypertension.

Answer

B. blood oxygen saturation of 95%.

Answer

C. left ventricular hypertrophy.

Answer

D. left to right shunt.

Answer

E. normal haemoglobin.

Question 37

The principal aim of a phase 1 trial of a cytotoxic agent is to:

Accepted Answer

E. establish the maximum tolerated dose (MTD).

Answer

A. maintain the patient’s hope that treatment is possible.

Answer

B. determine the best schedule of administration.

Answer

C. define tumour response rate.

Answer

D. measure progression-free survival.

Question 38

A 67-year-old woman with severe chronic obstructive pulmonary disease undergoes an all-night respiratory sleep study. The study reveals no evidence of obstructive sleep apnoea but there are three periods of repeated falls in oxyhaemoglobin saturation (SaO2).
Which one of the following is the most likely explanation for the falls in SaO2?

Accepted Answer

E. REMS-related reduction in respiratory drive.

Answer

A. SWS (slow wave sleep)-related upper airway narrowing.

Answer

B. REMS (rapid eye movement sleep)-related increase in nasal resistance.

Answer

C. REMS-related increase in ventilation-perfusion mismatching.

Answer

D. SWS-related reduction in cardiac output.

Question 39

Which one of the following is the strongest independent risk factor for stroke?

Accepted Answer

D. Age.

Answer

A. Hypertension.

Answer

B. Cigarette smoking.

Answer

C. Physical inactivity.

Answer

E. Hypercholesterolaemia.

Question 40

The diagram below shows cumulative quantal concentration-response curves for a hypothetical drug (drug X) which has linear kinetics. The Y-axis represents the percentage of the population studied who: for curve (a) achieved the desired therapeutic effect at a given plasma concentration; and for curve (b) experienced the most important toxic effect at a given plasma concentration.
If a patient with no evidence of toxicity who has not achieved the desired therapeutic response has a measured concentration of 40 mg/L, the best response would be to:

Accepted Answer

B. increase the dose by 25%.

Answer

A. check compliance with no change in dose.

Answer

C. increase the dose by 50%.

Answer

D. increase the dose by 75%.

Answer

E. increase the dose by 100%.

Question 41

A patient undergoes a Schilling test because of vitamin B12 deficiency. The following results are obtained:
The most likely pathology is:

Accepted Answer

B. pernicious anaemia.

Answer

A. small bowel bacterial overgrowth.

Answer

C. partial (Billroth II) gastrectomy.

Answer

D. terminal ileal Crohn’s disease.

Answer

E. short bowel syndrome.

Question 42

Which one of the following antibiotics is least active against pathogenic anaerobic bacteria (e.g. Bacteroides fragilis, Clostridium perfringens)?

Accepted Answer

D. Ceftriaxone.

Answer

A. Ticarcillin plus clavulanate.

Answer

B. Metronidazole.

Answer

C. Clindamycin.

Answer

E. Chloramphenicol.

Question 43

A 22-year-old woman has been on a stable dose of anticonvulsant for three years. She has recently experienced difficulties in seeing at night. A formal ophthalmological assessment demonstrates visual field constriction.
For which one of the following anticonvulsants is it important to monitor visual fields?

Accepted Answer

E. Vigabatrin.

Answer

A. Carbamazepine.

Answer

B. Gabapentin.

Answer

C. Lamotrigine.

Answer

D. Valproate.

Question 44

A 64-year-old woman undergoes a dual-energy X-ray absorptiometry scan. The report is shown below.
According to World Health Organisation (WHO) definitions, the patient's lumbar spine bone density is:

Accepted Answer

D. osteoporotic.

Answer

A. high normal.

Answer

B. normal.

Answer

C. osteopenic.

Answer

E. severely osteoporotic.

Question 45

A 48-year-old previously well man is receiving a transfusion of four units of packed red cell concentrate via a peripheral intravenous line after presenting with melaena secondary to a bleeding duodenal ulcer. He has not been previously transfused. Admission biochemistry (including urea, electrolytes and creatinine) is normal and pre-transfusion blood counts are normal apart from anaemia (haemoglobin 64 g/L [135-170]). Less than five minutes after transfusion of the third unit of blood is commenced, he complains of feeling very unwell and abruptly develops fever, chills, rigors and profound hypotension.
In the absence of ABO, Rhesus or minor blood group donor-recipient incompatibility, the most likely diagnosis is:

Accepted Answer

A. bacterial contamination of the transfused blood.

Answer

B. transfusion-associated graft-versus-host disease.

Answer

C. electrolyte disturbance.

Answer

D. citrate toxicity.

Answer

E. reaction to plasticiser in infusion bag.

Question 46

The following pharmacokinetic data (normalised to a 70 kg individual) are provided for five drugs.
Which one of the following drugs is most likely to have the slowest rate of clearance from plasma?

Accepted Answer

D. Tolbutamide.

Answer

A. Amiloride.

Answer

B. Amiodarone.

Answer

C. Dapsone.

Answer

E. Trimethoprim.

Question 47

A non-consanguineous family with a rare genetic disease has been identified. The pedigree is shown below.
What is the most likely mode of inheritance?

Accepted Answer

C. Autosomal dominant.

Answer

A. Mitochondrial.

Answer

B. X-linked.

Answer

D. Autosomal recessive.

Answer

E. Polygenic.

Question 48

Which one of the following findings during a stress exercise ECG test is most predictive of angiographically significant multivessel or left main coronary artery disease?

Accepted Answer

E. Failure to increase systolic blood pressure by at least 10 mmHg.

Answer

A. Late-onset of ST-segment depression.

Answer

B. Return to normal of ST-segment changes early in recovery phase.

Answer

C. ST-segment elevation in lead aVR.

Answer

D. Multifocal premature ventricular contractions.

Question 49

At the onset of infection or inflammation, the level of which one of the following acute phase proteins rises most rapidly and by the highest percentage over background?

Accepted Answer

D. C-reactive protein.

Answer

A. Fibrinogen.

Answer

B. Haptoglobin.

Answer

C. Transferrin.

Answer

E. Complement component 3 (C3).

Question 50

A 40-year-old woman presents with progressive breathlessness on exertion. She is a non-smoker. Physical examination and chest X-ray reveal no significant abnormality. Pulmonary function tests show the following results:
Which one of the following is the most likely explanation for this woman's pulmonary function test results?

Accepted Answer

A. Pulmonary vascular disease.

Answer

B. Pulmonary fibrosis.

Answer

C. Small airway disease.

Answer

D. Inadequate effort during the tests.

Answer

E. Hyperventilation syndrome.

Question 51

For an 82-year-old nursing home resident who experiences recurrent falls, which one of the following is least likely to prevent hip fracture?

Accepted Answer

C. Calcium supplements.

Answer

A. Oestrogen replacement therapy.

Answer

B. Bisphosphonates.

Answer

D. Balance and muscle strengthening exercises.

Answer

E. Hip protectors.

Question 52

The manometric feature most characteristic of achalasia is:

Accepted Answer

C. failure of lower oesophageal sphincter relaxation with swallowing.

Answer

A. lack of peristalsis in the oesophageal body.

Answer

B. high resting tone of the lower oesophageal sphincter.

Answer

D. poor propagation of oesophageal contraction waves.

Answer

E. diffuse spasm in the oesophageal body.

Question 53

Cytokine regulation (especially involving interleukin 2) is least affected by which one of the following immunosuppressive drugs?

Accepted Answer

B. Mycophenolate.

Answer

A. Prednis(ol)one.

Answer

C. Cyclosporin.

Answer

D. Tacrolimus (FK506).

Answer

E. Rapamycin.

Question 54

The mechanism of penicillin resistance in pneumococcal infections is most likely to be due to which one of the following?

Accepted Answer

D. Decreased affinity of penicillin-binding proteins.

Answer

A. Plasmid-mediated beta lactamase production.

Answer

B. Chromosome-mediated beta lactamase production.

Answer

C. Plasmid-mediated penicillinase production.

Answer

E. Altered permeability to penicillin.

Question 55

The most important application of carcinoembryonic antigen (CEA) measurements in patients with colon cancer is:

Accepted Answer

B. detection of resectable relapse.

Answer

A. testing of relatives.

Answer

C. determining prognosis of stage III disease.

Answer

D. identification of patients who require adjuvant chemotherapy.

Answer

E. monitoring during adjuvant treatment.

Question 56

In complex partial seizures of temporal lobe type, the most common finding at surgery for the epilepsy is:

Accepted Answer

A. mesial temporal sclerosis.

Answer

B. neuronal migration disorder.

Answer

C. old infarction.

Answer

D. normal brain.

Answer

E. cavernous angioma.

Question 57

The diagram below shows the relationship between the plasma concentration of a drug and the effect of that drug over time in a single individual given one dose of the drug. The direction of change over time is shown by the arrows. The relationship is described by an anti-clockwise hysteresis loop. The numbers on the loop indicate the number of hours after the dose was given.
The best explanation of this phenomenon is that:

Accepted Answer

E. there is a delay in the distribution of the drug from plasma to its site of action

Answer

A. the drug is binding irreversibly to its target receptor.

Answer

B. the drug is active itself but has no active metabolites.

Answer

C. there is a delay in the absorption of the drug from the gastrointestinal tract.

Answer

D. there is down-regulation of the drug’s target receptor over time.

Question 58

Genetically determined variation in which one of the following cell surface molecules is capable of conferring the greatest resistance to human immunodeficiency virus (HIV) infection?

Accepted Answer

B. Chemokine receptor CCR5.

Answer

A. Mannose-binding lectin.

Answer

C. Chemokine receptor CXCR4.

Answer

D. Human leucocyte antigen (HLA) class I.

Answer

E. Human leucocyte antigen (HLA) class II.

Question 59

Deficiency of which one of the following enzymes is most likely to cause severe hyperuricaemia?

Accepted Answer

D. Hypoxanthine-guanine phosphoribosyl transferase (HGPRTase).

Answer

A. Xanthine oxidase.

Answer

B. Adenosine deaminase.

Answer

C. Phosphoribosyl pyrophosphate (PRPP) synthetase.

Answer

E. Hexosaminidase

Question 60

Which one of the following physical findings would be least expected in association with the chest X-ray shown above?

Accepted Answer

A. A soft pulmonary component of the second heart sound (P2).

Answer

B. Prominent "v" wave in the jugular venous pressure.

Answer

C. Right ventricular lift.

Answer

D. Ejection click.

Answer

E. Early diastolic murmur

Question 61

Which feature of glomerular pathology is least consistent with the diagnosis of Wegener's granulomatosis?

Accepted Answer

C. IgG deposition.

Answer

A. Focal necrosis.

Answer

B. Crescents.

Answer

D. T cell infiltrate.

Answer

E. Macrophage infiltrate.

Question 62

A 62-year-old man on weekly oral methotrexate for psoriatic arthritis inadvertently receives a course of oral trimethoprim-sulfamethoxazole therapy for urinary infection. He becomes ill with mucositis, fever and bruising and is found to have moderately severe pancytopenia.
Folinic acid (in the form of calcium folinate) is administered intravenously as an antidote for presumed methotrexate toxicity.
The principal mode of action of folinic acid is:

Accepted Answer

E. provision of reduced folates for nucleic acid synthesis

Answer

A. enhanced renal excretion of methotrexate.

Answer

B. reduced intracellular accumulation of methotrexate.

Answer

C. conversion of methotrexate to an inactive metabolite.

Answer

D. activation of the enzyme dihydrofolate reductase.

Question 63

A young woman presents with thirst and polyuria. Following overnight water deprivation, which one of the following is the best indicator that she has partial (and central) diabetes insipidus rather than psychogenic polydipsia?

Accepted Answer

D. Increased urine osmolality in response to injected vasopressin.

Answer

A. Severe thirst.

Answer

B. Failure to reach normal urinary concentrations.

Answer

C. Low serum osmolality.

Answer

E. Increased blood urea.

Question 64

In the pedigree shown below, the man indicated by an arrow has been shown to have an autosomal recessive biochemical disorder with complete penetrance. The causative gene has not been identified. His parents are obligate carriers and do not exhibit any biochemical abnormalities. His sister also has normal biochemical studies. The carrier frequency in this population is 10%.
In the absence of consanguinity, what is the risk of the sister having a child with the biochemical abnormality?

Accepted Answer

B. 1 in 60.

Answer

A. 1 in 40.

Answer

C. 1 in 80.

Answer

D. 1 in 100.

Answer

E. 1 in 120.

2001a-Paper 1 – Medical Sciences

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