The following experiment is hypothetical. Meselson and Stahl labeled DNA with the heavy N15 isotope of nitrogen, then allowed the DNA to go through one round of replication in the presence of the light N14 isotope. After analyzing the resulting double stranded DNA helices in a CsCl density gradient they observed two bands of DNA in the gradient. One band was found in a position expected for DNA that had only the light N14 isotope, while the other band was found at the heavy N15 position. These observations are consistent with which mode of DNA replication?
a. dispersive replication
b. conservative replication
c. dispersive or semi-conservative replication
d. semi-conservative replication
Ans: b. conservative replication
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Which of the following accurately describe(s) ectotherms compared to endotherms of similar size at similar body temperatures? (Select all correct choices.)
A. Ectotherm metabolic rates are about 25% those of endotherms. B. Ectotherms cannot sustain prolonged activity for as long as endotherms can. C. Ectotherms can survive much longer periods without food than can endotherms. D. Ectotherm metabolic rates decrease as body temperature increases. E. Ectotherms never reach activity levels of endotherms.
The tradewinds in the zone from 0 to 30
degrees north latitude are generally from the a. north. b. northwest. c. northeast. d. southeast. e. southwest
Which of the following descriptions of Mendel is
INCORRECT? a. He was simply lucky to work out the laws of genetics. b. He focused on contrasting phenotypic characteristics. c. He demonstrated that the blending theory of inheritance was wrong. d. He kept exact mathematical data and was one of the first scientists to analyze results numerically. e. He was a monk, a science teacher, and a plant breeder.
Active immunity occurs after transfer of antibodies from mother to fetus. Indicate whether the statement is true or false