What are the functions of N, Cro, and Q in phage lambda?
What will be an ideal response?
Ans: N codes for an antitermination factor that allows transcription to proceed into the delayed early genes; Cro prevents synthesis of the repressor and it turns off expression of the immediate early genes; and Q is an antitermination factor that allows host polymerase to transcribe the late genes.
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What is a major difference between the extracellular matrix (ECM) of a plant cell and the ECM of an animal cell?
A) Plant ECM is composed primarily of proteins, whereas animal ECM is mainly carbohydrates. B) Plant ECM is primarily carbohydrate in nature, whereas animal ECM is mainly proteins. C) Plant and animal ECMs are quite similar in structure and function. D) ECM components in plant cells are released extracellularly by the Golgi stacks, whereas lysosomes do this in animal cells.
Boa constrictors on an island are an example of a(n) ______.
A. cell B. organ C. organism D. population E. ecosystem
A survey reveals that 25 percent of a population of 1,000 individuals have attached earlobes (are homozygous recessive for the trait). For the following questions, assume that the population fits the parameters of the Hardy-Weinburg law. Unlike most natural populations, this population is best characterized in which of the following ways?
a. There is genetic equilibrium. b. There is gene flow. c. There is genetic drift. d. Mutations occur. e. Mating is nonrandom.
Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber? 1. Tropomyosin shifts and unblocks the cross-bridge binding sites. 2. Calcium is released and binds to the troponin complex
3. Transverse tubules depolarize the sarcoplasmic reticulum. 4. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP. 5. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane. A) 1 ? 2 ? 3 ? 4 ? 5 B) 2 ? 1 ? 3 ? 5 ? 4 C) 2 ? 3 ? 4 ? 1 ? 5 D) 5 ? 3 ? 2 ? 1 ? 4