Give a reason why DNA makes a better material than RNA for the storage of genetic information, and explain your answer
What will be an ideal response?
Three possible answers are:
1. The deoxyribose sugar of DNA makes the molecule much less susceptible than RNA to breakage, because of the lack of the hydroxyl group on carbon 2 of the ribose sugar.
2. DNA is double-stranded and therefore the complementary strand provides a template from which damage can be repaired accurately.
3. The use of "T" in DNA instead of "U" (as in RNA) protects against the effect of deamination, a common form of damage. Deamination of T produces an aberrant base (methyl C), whereas deamination of U generates C, a normal base. The presence of an abnormal base eases the cell's job of recognizing the damaged strand.
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Which of the following statements regarding detection of shading in plants is not true?
A. Absorption of red light causes phytochrome to shift from its active state to its inactive state. B. Absorption of red light causes phytochrome to shift from its inactive state to its active state. C. Absorption of far-red light causes phytochrome to shift from its active state to its inactive state D. Absorption of red light causes a seed to germinate. E. Phytochrome is slowly shifted from its active state to an inactive state in the dark.
Which of the following is a feature shared by viruses and living organisms?
A) possession of a genome that directs synthesis of materials necessary for replication B) presence of cytoplasm C) metabolic capability D) responsiveness E) the ability to increase in size
How does the site of aerobic respiration in a cell compare with the site of anaerobic respiration?
A Both aerobic and anaerobic respiration occur in the cytoplasm. B Both aerobic and anaerobic respiration occur in the mitochondria. C Aerobic respiration occurs in the mitochondria, while anaerobic respiration occurs in the cytoplasm. D Aerobic respiration occurs in the cytoplasm, while anaerobic respiration occurs in the mitochondria.
Pain receptors are activated by tissue damage, but pain perception requires intact, functional neurons. How does this work?
A. The nociceptor neuron only sends action potentials as it is dying. B. The neuron itself does not need to be damaged; it responds to signals released by nearby damaged cells. C. Nociceptor neurons have special membrane repair mechanisms. D. The axon continues to fire action potentials despite damage to the cell body.