Suppose that some cells are grown in culture in the presence of radioactive nucleotides for many generations so that both strands of every DNA molecule include radioactive nucleotides. The cells are then placed in new medium with nucleotides that are not radioactive so that newly synthesized DNA will not be radioactive. What percentage of DNA molecules will contain radioactivity after 2 rounds of replication?
a) 0%
b) 25%
c) 50%
d) 75%
e) 100%
Ans: c) 50%
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Tacrolimus (FK-506) is a drug that inhibits an enzyme called calcineurin. Calcineurin is a protein phosphatase. This is an enzyme that dephosphorylates (removes phosphate groups) from proteins. When added to cells, tacrolimus can inhibit the dephosphorylation of a protein called NFAT, but it cannot prevent the dephosphorylation of a protein called CDK1. What is the most likely explanation for this finding?
A. Calcineurin requires an additional cofactor to dephosphorylate NFAT B. NFAT is a substrate of calcineurin, but CDK1 is not C. Tacrolimus is a competitive inhibitor of calcineurin for NFAT and CDK11 D. Tacrolimus changes the optimum pH for calcineurin Clarify Question What is the key concept addressed by the question? What type of thinking is required? Gather Content What do you already know about phosphates and enzymestructure? What other information is related to the question? Choose Answer Do you have all necessary information to analyze how tacrolimus works on NFAT and CDK1? Reflect on Process Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
Which cells in our body possess the MHC II protein?
A. Erythrocytes B. Neurons C. Thymus cells D. Macrophages E. Nasal epithelial cells
Which of the following vitamin deficiencies results in rickets?
a. vitamin A b. vitamin E c. vitamin D d. vitamin K
The somatic senses include all EXCEPT which
one of the following sensations? a. balance b. pain near the body surface c. temperature d. touch e. pressure