From the following set of statements regarding DNA topology, state whether each of the given statement is either True or False.

A.      The two strands of cccDNA can be easily separated without any breakage of bonds.

B.      Circular DNA molecules purified from bacteria and eukaryotes are usually negatively supercoiled.

C.      Interwound writhe and spiral writhe are topologically different.

D.      The organisms that live under extreme temperature conditions have been found to have positively supercoiled DNA.

E.      Negative supercoils can be thought of as a store of free energy that aids in processes that require strand separation.

#Question id: 4987

#Unit 11. Evolution and Behavior

A female fly, full of fertilized eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island, and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species each of which eats only a certain type of food. None of the species can fly, for their flight wings are absent, and their balancing organs (i.e., halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap.In each fly species, the entire body segment that gave rise to the original flight wings is missing. The mutation(s) that led to the flightless condition could have

#Question id: 4988

#Unit 11. Evolution and Behavior

If the foods preferred by each species are found on different parts of the island, and if the flies mate and lay eggs on their food sources, regardless of the location of the food sources, then the speciation events involving these fly species may have been driven, at least in part, by which of the following?

#Question id: 4989

#Unit 11. Evolution and Behavior

If the malesʹ halteres have species-specific size, shape, color, and use in courtship displays, and if the speciesʹ ranges overlap, then the speciation events may have been driven, at least in part, by which of the following?

#Question id: 4990

#Unit 11. Evolution and Behavior

Fly species W, found in a certain part of the island, produces fertile offspring with species Y. Species W does not produce fertile offspring with species X or Z. If no other species can hybridize, then species W and Y

#Question id: 4991

#Unit 11. Evolution and Behavior

Which of these fly organs, as they exist in current fly populations, best fits the description of an exaptation?

#Question id: 4992

#Unit 11. Evolution and Behavior

The existence of the phenomenon of exaptation is most closely associated with which of the following reasons that natural selection cannot fashion perfect organisms?