USMLE step 1 EXAM A+ GRADE ASSURED COMPLETE SOLUTIONS AND VERIFIED ANSWERS

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Exam Solution
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USMLE Step 1 uWorld High Yield Notes 2026 A+ GRAD
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E ASSURED COMPLETE SOLUTIONS AND VERIFIED ANS
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WERS (54FE3) zm




QUESTION 1 zm




What are the two major microtubular motor proteins? Which does anterograde axonal
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transport, which does retrograde axonal transport?
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ANSWER

Kinesin, Dynein Kinesin: Anterograde Dynein: Retrograde`
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QUESTION 2 zm




What do you think, immunologically speaking, when you see someone with recurrent
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Neisseria infections? zm




ANSWER

Inability to form the membrane attack (MAC) complex this is a common complement deficiency
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QUESTION 3 zm




What is the defect in Chronic Granulomatous disease? What is the pathophysiology?
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ANSWER

NADPH Oxidase deficiency leads to the inability to kill intracellular organisms
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QUESTION 4 zm




Characteristic triad of ataxia telangiectasia? zm zm zm zm




ANSWER

cerebellar ataxia, telangiectasias, increased risk of sinopulmonary infections
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,QUESTION 5 zm




What is the major immune deficiency of ataxia telangiectasia?
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ANSWER

IgA deficiency, which predisposes to infections of the upper and lower airways (and other mucous
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membranes)



QUESTION 6 zm




There's a useful mnemonic for Ataxia Telangiectasia and the gene that's mutated. Wha
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t is it?
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ANSWER

ATM Ataxia Telangiectasia Mutated ATM gene is responsible for DNA break repair
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QUESTION 7 zm




What is one reason that lead intoxication causes hypochromic anemia?
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ANSWER

Mitochondrial iron transport is important for Heme synthesis! It's inhibited by lead. So you don't ma
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ke heme in your mitochondria and you get hypochromic anemia.
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QUESTION 8 zm




What is the biochemical problem in Lesch-
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Nyhan syndrome? (And, only if you got that right, what are the really cool symptoms
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of it?)
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ANSWER

Defective purine catabolism, so buildup of purines. It's an X-
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linked recessive disorder with mutated HGPRT gene (hypoxanthine-
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guanine phosphoribosyltransferase, if you want to impress people). Now, if you got HGPRT and puri
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ne catabolism right, you can say: self-
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mutilating behavior on top of mental retardation, choreoathetoid (think Chorea) movements and spa
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sticity.



QUESTION 9 zm




What is the defect in Niemann-
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Pick disease? What causes that? What is the common macular finding?
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ANSWER

,Sphingolipid degradation is defective Caused by an autosomal recessive defect in sphingomyelinase C
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herry Spot on the macula? Niemann Pick's or Tay Sach's.
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QUESTION 10 zm




If a baby gets exposed to an unclean knife (...) and subsequently develops rigid paraly
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sis, what is the diagnosis, where do we think this might happen, and how do we prev
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ent it?zm




ANSWER

Neonatal Tetanus Developing Countries Maternal immunization with tetanus toxoid is the best way t
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o prevent it an adeuately immunized mom will transfer IgG's across the placenta to the neonate
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QUESTION 11 zm




Which microtubule associated protein aids in anterograde transport of intracellular ve
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sicles and organelles? Which end of the microtubule do they go towards?
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ANSWER

Kinesin. Towards the (+) rapidly growing end.
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QUESTION 12 zm




What is an early BRAIN finding of Ataxia-
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Telangiectasia and how does it manifest itself? zm zm zm zm zm zm




ANSWER

Cerebellar atrophy manifests as ataxia in the first years of life.
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QUESTION 13 zm




High yield path association for Alzheimer's disease?
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ANSWER

Neurofibrillary tangles in the neocortex zm zm zm zm




QUESTION 14 zm




High yield path association for Parkinson's disease?
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ANSWER

Loss of neurons in the substantia nigra
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, QUESTION 15 zm




High yield path association for Huntington disease?
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ANSWER

Atrophy of caudate nucleus
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QUESTION 16 zm




What are the major manifestations of Ataxia-telangiectasia?
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ANSWER

cerebellar ataxia, oculocutaneous tenlangiectasias, repeated sinopulmonary infections, and an increas
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ed incidence of malignancy
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QUESTION 17 zm




If you heard: amenorrhea, bitemporal hemianopsia, and enlargement of the pituitary g
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land on brain imaging, what would you be thinking?
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ANSWER

Prolactinoma, the most common pituitary adenoma.
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QUESTION 18 zm




What embryological layer is the anterior pituitary derived from?
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ANSWER

Surface ectoderm zm




QUESTION 19 zm




What is the most common congenital abnormality associated with the use of Sodium V
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alproate during pregnancy? zm zm




ANSWER

neural tube defects, e.g., meningocele because valproate inhibits intestinal folic acid absorption result
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ing in teratogenicity
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QUESTION 20 zm




What is the characteristic histology of a craniopharyngioma?
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