Question

DNA synthesis is the joining of _______?

Nucleotides can only be added from what end?
Therefore DNA synthesis occurs in what direction?
What provides the energy for the formation of each new phosphodiester bond?
A) Nucleotides, 3' end, 5' to 3', ATP hydrolysis
B) Amino acids, 5' end, 3' to 5', GTP hydrolysis
C) Nucleotides, 5' end, 3' to 5', ATP hydrolysis
D) Amino acids, 3' end, 5' to 3', GTP hydrolysis

Answer 1

DNA synthesis involves the joining of nucleotides at the 3' end of the growing strand, proceeding from 5' to 3' direction, with the energy provided by ATP hydrolysis.

Step-by-step explanation:

DNA synthesis is the joining of nucleotides. Nucleotides can only be added to the 3' end of a growing DNA strand. Therefore, DNA synthesis occurs from 5' to 3' direction. The energy for the formation of each new phosphodiester bond comes from the hydrolysis of ATP. Hence, the correct answer to the question is A) Nucleotides, 3' end, 5' to 3', ATP hydrolysis.

During this process, the enzyme DNA polymerase adds new nucleotides to the 3' end of the nascent (newly synthesizing) DNA strand by forming a phosphodiester bond between the 3'-OH end of the existing strand and the 5' phosphate of the incoming nucleotide. This bond formation releases two phosphate groups as pyrophosphate, which is subsequently hydrolyzed, providing the energy necessary for the polymerization to continue. DNA polymerases require a free 3'-OH group to initiate the synthesis; this is made available by an RNA primer that is laid down by the enzyme RNA primase.