MCQ corner

Abstract

1. Selenocysteine is coded by UGA UAG UAA AUG Ans: A. UGA Explanation Selenocysteine (SeCys/SeC) is the 21st amino acid and is found in thioredoxin reductase, glutathione peroxidase, 5’-deiodinase, and selenoprotein P. It is an exceptional case where a stop codon codes for an amino acid. The other stop codons are UAA and UAG. The ability of the protein synthetic apparatus to identify a selenocysteine-specific UGA codon involves the selenocysteine insertion element, a stem-loop structure in the untranslated region of the mRNA.[1] 2. A child with diarrhea for 2 days came to your out-patient department (OPD). On examination, the signs of dehydration were marked and the child was treated with oral rehydration solution (ORS). Glucose absorption was facilitated by which receptors? SGLT1 SGLT2 GLUT4 Sodium–hydrogen antiporter Ans: A. SGLT1 Explanation Absorption of glucose from the intestinal lumen to intestinal cells is by the cotransport mechanism. It is an active transport system and can transport against the concentration gradient.[2] 3. Skeletal derivative of the second pharyngeal arch is Malleus Incus Stapes Maxilla Ans: C. Stapes Explanation Maxilla, malleus, and incus are derived from the first arch.[3] 4. Blastocyst makes contact with a uterus on <3 days 5–7 days 8–11 days 15–16 days Ans: B. 5–7 days Explanation Contact of the blastocyst with endometrium occurs at the time of implantation. Implantation occurs at around 5-7 days.[4] 5. The father of antiseptic surgery is Louis Pasteur Robert Koch Julius Petri Joseph Lister Ans. D. Joseph Lister Explanation Louis Pasteur – the father of microbiology, Robert Koch – the father of microbiology (with Louis Pasteur), and the father of medical bacteriology, Julius Petri – invented the Petri dish.[5] 6. Following were the findings in a Glucose tolerance test (GTT). Fasting blood glucose <75 mg/dl; all blood samples show low blood glucose; urine glucose – nil. The possible diagnosis is Alimentary glycosuria Diabetes mellitus Hypopituitarism Diabetes insipidus Ans. C. Hypopituitarism Explanation In alimentary glycosuria, there will be a peak in the first sample after glucose load and sugar will appear in urine. In diabetes mellitus, fasting and the next two samples will show higher values than the normal reference range and the sample does not return to baseline at the end of the test. In hypopituitarism, there is hypoglycemia and the patient feels fatigued and stressed. In diabetes insipidus, GTT is mostly unaffected.[6] 7. A 10-year-old boy with a history of atopy presented with seasonal recurrent bilateral conjunctivitis and complained of blurred vision for the past 1 week. On lid eversion, giant papillae were seen. All of the following could be seen by slit-lamp examination except: Vascular pannus and punctate epithelial erosions involving the superior cornea. An oval epithelial ulceration with underlying stromal opacification in the central cornea Limbal follicles Conjunctival symblepharon Ans. D. Conjunctival symblepharon Explanation A conjunctival symblepharon is seen in the case of autoimmune disorders such as Sjogren’s syndrome, sarcoidosis, lichen planus, granulomatosis with polyangiitis, etc.[7] 8. Which of the following breast lesion is a noninvasive malignancy? Tubular carcinoma and mucinous carcinoma Intraductal carcinoma of the comedo type Infiltrating ductal carcinoma and lobular carcinoma Medullary carcinoma, including atypical medullary lesions Ans. B. Intraductal carcinoma of the comedo type Explanation A comedo-type ductal carcinoma in situ (DCIS), also known as comedocarcinoma insitu, is the high-grade subtype of DCIS. It completely fills and dilates the ducts and lobules in terminal duct lobular units with plugs of high-grade tumor cells with central necrosis “comedonecrosis.”[8] 9. In patients who develop a documented episode of deep-vein thrombosis, the most significant long-term sequelae are: Claudication Recurrent foot infections Development of stasis ulcer Pulmonary embolization Ans. C-Development of stasis ulcer Explanation Chronic symptoms may occur after 6 weeks or beyond. Pulmonary embolization is the most common complication but is seen as an acute complication.[9] 10. Identify the test from the diagram. Rothera’s test Benedict’s test Barfoed’s test Seliwanoff’s test Ans. A. Rothera’s testFigure 1: Purple permanganate coloured ring [Ferro-penta cyanine complex] at the junction of two fluidsExplanation Rothera’s test was done to identify the presence of ketone bodies in a urine sample. Benedict’s test will contain a green/yellow/orange/brick red precipitate at the bottom. Barfoed’s test has a red scum at the top of the fluid and a little red precipitate at the bottom. Seliwanoff’s test will have a cherry red color.[10] Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.