A boy developed signs of sexual maturity at age 3. A possible diagnosis is
A) XY female syndrome.
B) XX male syndrome.
C) congenital adrenal hyperplasia due to 21-hydroxylase deficiency.
D) pseudohermaphroditism due to 5-alpha reductase deficiency.
C) congenital adrenal hyperplasia due to 21-hydroxylase deficiency.
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Consider a mutant organism that is unable to make the amino acid arginine. Knowing that the
metabolic pathway to production of arginine is ornithine ? citrulline ? arginosuccinate ? arginine, you test the ability of the mutant to grow in the presence of each one of these compounds, providing just one of the compounds in each of your tests. You find that the mutant can grow in the presence of arginosuccinate or arginine, but not in the presence of citrulline or ornithine. From this you can conclude that the product of the gene mutated in the mutant is most directly involved in production of ____.
a. arginine from ornithine b. arginosuccinate from citrulline c. citrulline from ornithine d. arginine from arginosuccinate e. arginosuccinate from ornithine
Which tissue has little extracellular matrix, acts as an insulator, and is used to store chemical energy?
a. loose connective tissue b. blood c. cartilage d. fibrous connective tissue e. adipose tissue.
If you transfuse type AB blood into a patient with type A blood, the patient will raise antibodies against the B antigen on the donor's blood, but will not raise antibodies against the A antigen. Why not?
A. B and T cells that recognize the A antigen will have been removed by clonal deletion. B. Antibodies that recognize the A antigen will have been removed by the spleen. C. Antibodies that recognize the A antigen will have been removed by the bone marrow. D. Macrophages will not present the A antigen to T cells. E. Recombination of the gene for antibodies cannot produce self-reactive clones.
Which of the following vitamins is incorrectly paired with its known function?
a. vitamin C?antioxidant b. vitamin K?essential for blood clotting c. folic acid?coenzyme for synthesis of nucleic acids d. vitamin A?converted to retinal e. panthothenic acid–promotes calcium absorption