Consider the following diagrams showing a replication fork moving from left to r
ID: 100820 • Letter: C
Question
Consider the following diagrams showing a replication fork moving from left to right. The thick lines represent the template/parental strands. The 5' and 3' represent the ends of those template/parental strands. Refer to Exhibit 10A. Which Okazaki fragment was synthesized earliest? a. A b. B c. C d. D The energetic driving force for nucleic acid synthesis is a. removal of pyrophosphate from the incoming nucleotide. b. removal of pyrophosphate from the growing strand. c. removal of inorganic phosphate from the incoming nucleotide. d. removal o f inorganic phosphate from the growing strand. DNA polymerase III from E. coli a. is a large, multisubunit protein b. has a sliding clamp portion that anchors it to DNA c. has a polymerization site separate from the DNA binding site d. all of theseExplanation / Answer
1. 1. Okazaki fragments are pieces of DNA that are transient components of lagging strand DNA synthesis at the replication fork. One strand is opened in the 5' - 3' direction, which is the forward direction, and is called the leading strand. The other strand is opened in the 3' - 5' direction, which is the reverse direction, and is called the lagging strand. Both the Okazaki fragments and the leading strand are synthesized in the 5 3 direction. The discontinuohus assembly of the lagging strand enables 5 3 polymerization at the nucleotide level to give rise to overall growth in the 3 5 direction.Ans: a
2. Hydrolysis of pyrophosphate is the driving force for DNA synthesis.
Additional free energy is provided by the rapid hydrolysis of the pyrophosphate into 2 phosphate groups by an enzyme known as pyrophosphatase. Ans: a
3. DNA polymerase III is a holoenzyme, which has two core enzymes (Pol III), each consisting of three subunits (, and ), a sliding clamp that has two beta subunits, and a clamp-loading complex which has multiple subunits (, , , , and ). Ans: d