Question

question 42
1 pts
a rapidly dividing cell is exposed to a chemical that converts the bond that forms between adenine and thymine to a covalent bond. which of the following is most likely to occur?
o dna replication would not occur because the two nucleotide strands that make up the dna molecule would not be able to separate.
o dna replication would produce two molecules of dna with mutations at every base that once held an a - t base pair.
o dna replication would occur more slowly because dna repair proteins would have to fix the covalent bonds before replication could begin.
o dna replication would be faster because covalent bonds require less energy to break than hydrogen bonds.

Explanation:

In DNA replication, the double - helix structure must unwind. Normally, adenine (A) and thymine (T) are held together by hydrogen bonds, which are relatively weak and can be easily broken to separate the DNA strands. If the bond between A and T is converted to a covalent bond (which is much stronger), the two nucleotide strands that make up the DNA molecule would not be able to separate. Without strand separation, DNA replication (which requires access to the template strands) cannot occur.

• For the option “DNA replication would produce two molecules of DNA with mutations at every base that once held an A - T base pair”: There is no indication that the covalent bond would cause a mutation in the base - pairing itself. The problem is with strand separation, not base - pair alteration.
• For the option “DNA replication would occur more slowly because DNA repair proteins would have to fix the covalent bonds before replication could begin”: DNA repair proteins are not typically involved in fixing bonds between normal base - pairs (A - T) during the normal replication process. The main issue is strand separation, not a “repair” of a normal base - pair bond.
• For the option “DNA replication would be faster because covalent bonds require less energy to break than hydrogen bonds”: Covalent bonds actually require more energy to break than hydrogen bonds. So this statement is factually incorrect.

Answer:

DNA replication would not occur because the two nucleotide strands that make up the DNA molecule would not be able to separate.