A new DNA strand elongates only in the 5' to 3' direction because: a. DNA polymerase can add nucleotides only to the free 3' end. b. The polarity of the DNA molecule prevents addition of nucleotides at the 3' end. c. Okazaki fragments prevent elongation in the 3' to 5' direction. d. DNA polymerase begins adding nucleotides at the 5' end of the template. e. Replication must progress toward the replication fork.
Biology · High School · Mon Jan 18 2021
Answered on
a. DNA polymerase can add nucleotides only to the free 3' end.
The correct option is (a) because DNA polymerase enzymes, which are responsible for catalyzing the formation of the DNA strand, can only add DNA nucleotides to the free 3' hydroxyl (-OH) group of the growing strand. This is a fundamental aspect of the enzyme's functionality and is a result of the chemical properties of DNA and the enzymes involved. DNA polymerases work by binding nucleotides (the building blocks of DNA) that are complementary to the template strand, with each new nucleotide being added to the 3' end of the newly forming strand, thus causing the strand to elongate in a 5' to 3' direction.