Watson and Crick proposed that during DNA replication the double helix is unwound and each parental DNA strand is used as a template to generate a new daughter strand. What is this mode of replication called?
A. conservative replication
B. semiconservative replication
C. dispersive replication
D. discontinuous replication
E. continuous replication
Describing the protein causing red blood cells to be sickle-shaped is referring to the protein's:
A. phenotypic function
B. cellular function
C. molecular function
Multiple models were proposed to explain replication. What experimental approach allowed researchers to distinguish between them?
A. Cells were pulsed with high specific activity 3H thymidine to show the direction of DNA synthesis on the chromosome.
B. Cells infected with T4 bacteriophage were grown in the presence of radioactive nucleotides. When DNA was analyzed in alkaline CsCl gradients, the presence of short DNA fragments indicated that discontinuous replication had occurred.
C. Bacteria were grown on 15NH4 until the entire DNA contained heavy nitrogen and then the cells were transferred to normal, light media for one round of replication. The resulting DNA molecules were separated in density gradients and compared to the expected results for each proposed model.
D. Bacteria were grown on 3H thymidine until the entire DNA contained heavy thymidine and then the cells were transferred to normal, light media for one round of replication. The resulting DNA molecules were separated in density gradients and compared to the expected results for each proposed model.
E. None of these choices is correct.
The supersecondary structure (motif) most likely to contain a heptad (or leucine) repeat would be:
A. a Greek key.
B. a --.
C. a helix-turn-helix.
D. a coiled-coil.
E. a four-helix bundle.
Which of the following is not a correct description of DNA replication in bacteria?
A. DNA replication is semiconservative.
B. DNA replication is discontinuous.
C. DNA replication is dispersive.
D. DNA replication begins at origins of replication and proceeds bidirectionally.
E. DNA replication is semiconservative and dispersive.
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