Histology: Clinical Correlations for NBME Questions With 100% Correct Answers

Down syndrome Correct Answer (trisomy 21) is characterized by mental retardation, short stature, stubby appendages, congenital heart malformations, and other defects. Klinefelter syndrome Correct Answer (XXY) is aneuploidy of the sex chromosomes, characterized by infertility, variable degrees of masculinization, and small testes. Turner syndrome Correct Answer (XO) is monosomy of the sex chromosomes, characterized by short stature, sterility, and various other abnormalities. Transformed cells Correct Answer Transformed cells have lost their ability to respond to regulatory signals controlling the cell cycle. They may undergo cell division indefinitely, thus becoming cancerous Vinca alkaloids Correct Answer arrest these cells in mitosis; drugs that block purine and pyrimidine synthesis may arrest cells in the S phase of the cell cycle. Cholera toxin Correct Answer exotoxin produced by the bacterium Vibrio cholerae that alters Gs protein so that it is unable to hydrolyze its GTP molecule. As a result, cAMP levels increase in the surface-absorptive cells of the intestine, leading to excessive loss of electrolytes and water and severe diarrhea. Pertussis toxin Correct Answer Pertussis toxin,the product of the bacterium that causes whooping cough, inserts ADP-ribose into the subunits of trimeric G proteins, causing the accumulation of the inactive form of G proteins resulting in irritation of the mucosa of the bronchial passages Defective Gs proteins Correct Answer may lead to mental retardation, diminished growth and sexual development, and decreased responses to certain hormones. Venoms Correct Answer Venoms,such as those of some poisonous snakes, inactivate acetylcholine receptors of skeletal muscle sarcolemma at neuromuscular junctions. Hereditary spherocytosis Correct Answer 1. Hereditary spherocytosisresults from a defective spectrin that has a decreased ability to bind to band 4.1 protein. The disease is characterized by fragile,misshapen red blood cells, or spherocytes; destruction of these spherocytesin the spleen leads to anemia. 2. During high-speed car accidents and often in shaken baby syndrome, the sudden accelerating and decelerating forces applied to the brain cause shearing damage to