When does lactase production begin to decline in humans?
a. Age 55
b. Age 5
c. Age 25
d. Never
e. Age 46
b
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Which of the following is a possible reason why DNA uses thymine instead of uracil?
A. Thymine is more stable than uracil. B. Cytidine is deaminated to uracil so it would be difficult for any repair mechanism to differentiate between uracil that belongs in the sequence and uracil that resulted from deamination. C. Adenine is deaminated to uracil so it would be difficult for any repair mechanism to differentiate between uracil that belongs in the sequence and uracil that resulted from deamination. D. When uracil is bound to a deoxyribose it will become more reactive, forming covalent bonds with other bases. E. None of these choicesis correct.
A new laboratory assistant was asked to disinfectant the laboratory bench where specimens are received and processed. The laboratory assistant used concentrated bleach to wipe down the la-boratory bench. The discrepancy in this situation is:
a. the laboratory assistant forgot to rinse the laboratory bench after disinfecting it. b. the laboratory assistant failed to wash the laboratory bench with soap prior to ap-plying the bleach. c. the laboratory assistant failed to use di-luted 10% bleach, thinking that concen-trated solution will result in improved disinfection of the bench. d. the laboratory assistant followed proper procedure and there is no discrepancy.
Which of the following is a hemorrhagic fever?
A. Cat-scratch fever B. Chikungunya C. Q fever D. Trench fever E. Rocky Mountain spotted fever
Oxyhemoglobin contains _____
a. oxygen bound irreversibly to a heme group b. carbon dioxide c. carbonic anhydrase d. bound oxygen in the absence of a heme group e. oxygen bound reversibly to a heme group