DNA replication Transitional Reasoning Download PDF

Questions

1. 1.

   In an in vitro bacterial DNA replication assay, leading-strand synthesis proceeds normally, but the lagging strand produces fragments that persistently retain RNA segments covalently joined at their 5' ends. The researchers determine that this defect is caused by the loss of 5' to 3' exonuclease activity in the processing polymerase. Which statement correctly explains why this specific enzymatic activity is required to complete lagging-strand synthesis?

   • A) It breaks the hydrogen bonds between parental strands to enable continuous replication fork progression.
   • B) It catalyzes phosphodiester bond synthesis between adjacent Okazaki fragments without requiring ATP hydrolysis.
   • C) It degrades ribonucleotide primers from the 5' end so that DNA polymerase can replace them with deoxyribonucleotides.
   • D) It synthesizes short complementary RNA oligonucleotides that provide the free 3'-OH groups needed for fragment initiation.