For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate
They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work? A) There is no radioactive isotope of nitrogen.
B) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.
C) Although there are more nitrogens in a nucleotide, labeled phosphates actually have sixteen extra neutrons; therefore, they are more radioactive.
D) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
D
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Red-green color blindness is a sex-linked recessive trait in humans. If a carrier female (heterozygous for the trait) mated with an affected man, what would be the expected outcome(s)?
A. None of the offspring would be color blind. B. None of the daughters would be color blind. C. Half of the daughters would be color blind. D. All of the sons would be color blind. E. Half of the daughters would be color blind, and all of the sons would be color blind.
The area covered by tropical rain forest is reduced by millions of hectares per year due to agriculture and logging. Which of the following best describes a likely result of tropical rain forest deforestation?
(A) Populations of plants and animals will decrease as more rain forest disappears, leading to a decrease in biodiversity. (B) An increase of soil moisture will lead to a rapid increase in new vegetation coverage. (C) An increase in atmospheric carbon dioxide will lead to higher levels of ultraviolet radiation reaching the surface of Earth. (D) More oxygen will be available to other organisms as plant numbers decrease.
Suppose you are a genetic counsellor, and a man and woman come to you with concerns that if they have a child together, it could have hemophilia. Also suppose that the man has an X-linked recessive form of hemophilia, but the woman does NOT, and that genetic tests reveal the woman is NOT a carrier for hemophilia. Which of the following is the best advice you could give them?
a. Each child that they produce will have a 50% chance of having hemophilia. b. None of their offspring should have hemophilia, but each of their female offspring will be carriers for hemophilia. c. Each of their male offspring will have a 50% chance of having hemophilia; and while their female offspring should not have hemophilia, they will each have a 50% chance of being carriers. d. Each of their male offspring will have hemophilia, and each of their female offspring will have a 50% chance of
The outbreak of typhoid in connection with Typhoid Mary led to which epidemiogic findings?
a. the importance of tracking disease carries b. the use of antibiotics for treating typhoid c. the use of exercise for treating typhoid d. the importance of hand washing to prevent disease