If our bodies are capable of secondary responses, how do people contract influenza more than once?
a. Memory cells lose their ability to recognize antigens after six months.
b. The affinity of antibodies diminishes in the secondary response.
c. New varieties of flu virus continuously evolve.
d. Our bodies cannot launch a strong enough immune response against the flu virus.
e. There are no effective vaccinations for the flu.
C
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H1 binding to DNA is different than that of the other four histones because H1 binds to:
A. the major groove of the DNA only. B the DNA as it comes off both sides of the nucleosome. C. as a component of the octamer; however, unlike H2A, H3, and H4, H1 lacks the histone tail. D. one strand of the linker DNA as it comes off the nucleosome and binds a second site in the central region of the DNA supercoil. E. the DNA as a homotetramer.
Which factor(s) determine a species' optimal foraging theory?
a. availability of parasites b. availability of predators c. energy needed to capture food and court mates d. energy that foraging provides e. energy needed to capture food and the energy that the food provides
What property of water allows it to stick to objects and make them wet?
What will be an ideal response?
The following events are associated with muscle contraction. Which one of the following best describes the order in which these events occur, following the initiation of a contraction by a nerve impulse?
1. T tubules transmit electrical impulses throughout the muscle cell. 2. Myosin contacts actin and pulls it toward the center of the sarcomere. 3. Acetylcholine binds to receptors on the muscle. 4. Troponin-tropomyosin complex shifts to expose myosin binding sites. 5. Calcium is released from the sarcoplasmic reticulum. A) 3, 1, 5, 4, 2 B) 1, 3, 5, 2, 4 C) 3, 5, 1, 2, 4 D) 4, 2, 1, 3, 5 E) 3, 5, 1, 4, 2