For a lambda phage in lysogeny, why is a repressor protein required to block the lytic cycle from the beginning?
What will be an ideal response?
Ans: A repressor is required because the early genes can be transcribed by the host's RNA polymerase; the default state would be constitutive expression of these genes.
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Paired, fleshy extensions of the body wall in bristle worms that are used for locomotion and gas
exchange are called
a. metanephridia. b. parapodia. c. septa. d. clitella. e. setae.
Which is a disadvantage of air as a respiratory medium?
a. Air evaporates water from the respiratory surface. b. Air contains 30 times as much O2 as water. c. Air is 1000 times less dense than water. d. Air requires less energy to ventilate over the respiratory surface. e. O2 diffuses more rapidly in air than in water.
A P. bursaria cell that has lost its zoochlorellae is said to be aposymbiotic. It might be able to replenish its contingent of zoochlorellae by ingesting them without subsequently digesting them
Which of the following situations would be most favorable to the reestablishment of resident zoochlorellae, assuming compatible Chlorella are present in P. bursaria's habitat? A) abundant light, no bacterial prey B) abundant light, abundant bacterial prey C) no light, no bacterial prey D) no light, abundant bacterial prey
Which of the following is used by phylogenetic biologists to determine how organisms are related evolutionarily?
A. DNA analysis B. fossils C. comparative studies of the anatomy of organisms D. All of these answers are correct.