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TLS Online TPP Program

#Question id: 760

Which force can stabilize a DNA double-helix?

#Unit 1. Molecules and their Interaction Relevant to Biology

  1. Hydrophobic bases are found in the interior of the helix where each base pair is stabilized by the same number of hydrogen bonds.

  2. Hydrophilic sugar-phosphate groups are found on the exterior of the helix where they can interact with water.

  3. Non-covalent N-glycosidic bonds can form between nitrogenous bases in opposite strands in the helix.

  4. Covalent base-stacking interactions can occur between adjacent bases within the same strand in the helix.

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TLS Online TPP Program

#Question id: 8840

#Unit 9. Diversity of Life Forms

There are at least a dozen known species in the extinct genus Lystrosaurus. If each species was suited to a quite different environment, then this relatively large number of species is likely due to
TLS Online TPP Program

#Question id: 8903

#Unit 9. Diversity of Life Forms

Terry detaches the snakelike organism from the fish and uses a knife to cut off its head. In doing so, its brain slides out onto the deck of the boat. Terry peers into the cut end of the head and notices that the brain had lain in a sort of pan-like structure that only partially surrounded the brain. What is the structure Terry is observing, and what is it made of?
TLS Online TPP Program

#Question id: 8900

#Unit 9. Diversity of Life Forms

Which of the following statements about craniates is (are) correct?
1. Craniates are more highly cephalized than are non-craniates.
2. Craniatesʹ genomic evolution includes duplication of clusters of genes that code for transcription factors.
3. The craniate clade is synonymous with the vertebrate clade.
4. Pharyngeal slits that can assist in gas exchange originated in craniates,
5. The two-chambered heart originated with the early craniates.
TLS Online TPP Program

#Question id: 8899

#Unit 9. Diversity of Life Forms

A new species of aquatic chordate is discovered that closely resembles an ancient form. It has the following characteristics: external armor of bony plates, no paired lateral fins, and a suspension-feeding mode of nutrition. In addition to these, it will probably have which of the following characteristics?
TLS Online TPP Program

#Question id: 8893

#Unit 9. Diversity of Life Forms

While sampling marine plankton in a lab, a student encounters large numbers of fertilized eggs. The student rears some of the eggs in the laboratory for further study and finds that the blastopore becomes the mouth. The embryo develops into a trochophore larva and eventually has a true coelom. These eggs probably belonged to a(n)
TLS Online TPP Program

#Question id: 8891

#Unit 9. Diversity of Life Forms

While vacationing in a country that lacks adequate meat inspection, a student ate undercooked ground beef. Sometime later the student became easily fatigued, and lost body weight. At about the same time, whitish, flattened, rectangular objects full of small white spheres started appearing in his feces. Administration of niclosamide cured the problem. The student had probably been infected by a