USMLE WORLD STEP 1 PRACTICE TEST TRIAL

In this case, random inactivation of an X chromosome leads to different genotypes expressed in patches.

Mosaicism occurs when there are cell lines containing two or more different genetic makeups leading to different phenotypes. Which of the following best describes the mechanism by which hepatitis B facilitates infection by hepatitis D virus?Д«)В Production of proteins that coat HDV viral particlesД®)В Upregulation of HDV receptors on hepatocytesД¬orrect Answer: DThis is an example of mosaicism. A hepatitis panel confirms the diagnosis of hepatitis D infection. Laboratory results are remarkable for severely elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as well as elevated total bilirubin. She has a past medical history significant for chronic hepatitis B infection, which has been stable, and a long-standing history of intravenous drug abuse. Laboratory examination shows: BUN 13 mg/dL Creatinine 0.8 mg/dL WBC 8,000 cells/mm3 Platelets 24,000 platelets/mm3 Hemoglobin 14.1 mg/dL Hematocrit 42% PT 14 seconds (normal 11-15 seconds) aPTT 27 seconds (normal 25-40 seconds) Bleeding time 11 minutes (normal 2-7 minutes) What is the most likely diagnosis for this patientвЂ™s condition?ДЄ 30-year-old female presents with abdominal pain, nausea, vomiting that began two days ago. Abdominal exam is negative for splenomegaly. On dermatologic examination, she has diffuse areas of petechiae under her tongue, on the extensor surfaces of her forearms, and on her posterior thighs bilaterally, none of which are elevated or palpable. On examination, she is afebrile, has a pulse of 78 beats/minute and a blood pressure of 119/82. She denies headaches or changes in vision.

She has never been pregnant but notes that her menstrual periods have been вЂњmore heavy than usualвЂќ during the same 6 months. She has no past medical or surgical history and takes no medications. She has experienced approximately two to three epistaxis episodes per month during this period, and the bleeds eventually stops following packing of the anterior nares. Q:В A 34 year-old woman presents to the emergency department with a 6-month history of recurrent epistaxis and easy bruising. What is the best treatment for this clinical presentation? Laboratory assessment is as follows: Hemoglobin 14.5 mg/dL Hematocrit 47% WBC 7,400 cells/mm3 Platelets 180,000 cells/mm3 Ultrasonography confirms the diagnosis. A stool sample appears as вЂњcurrant jellyвЂќ and is positive for blood. Right upper and lower quadrant tenderness can be elicited on palpation without rebound tenderness or tympany, and a sausage-shaped mass can be palpated in the right lower quadrant. He has a heart rate of 114 beats/minute, a respiratory rate of 22 breaths/minute, a blood pressure of 104/79 mmHg, and a temperature of 36.4oC. Q:В A 14-month-old male child with no past medical history is brought to the emergency department with vomiting, colicky abdominal pain, and several bowel movements containing both blood and mucus. This is an example of which of the following? In female cats that inherit X chromosomes with different alleles, the resulting coat has patches of each color due to random inactivation of a single X chromosome. He believes that the gene for fur color is carried on the X chromosome. When an orange male cat is mated with a black female cat, all the male cats are black but female cats have patches of orange and black. When a black male cat is mated with an orange female cat, all the male cats are orange but the female cats have patches of orange and black. Likewise, when two orange cats are mated, the resulting offspring are orange. He notes that when two cats that are black are mated, all the offspring are black. He has cats that are black and cats that are orange. Q:В A veterinary student is studying the genetics behind inheritance of coat colors in cats. USMLE Step 1 Practice Questions from TrueLearn:

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USMLE WORLD STEP 1 PRACTICE TEST TRIAL

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Usmle world step 1 practice test