Question

The descriptive phrase 5' to 3' refers to ___

a. the right to left action of Okazaki fragments.
b. an arbitrary but understood numbering of the carbon atoms in cytosine.
c. an arbitrary but understood numbering of the purine molecules.
d. an arbitrary but understood numbering of the carbon atoms in the deoxyribose.
e. the left to right action of DNA ligase.

Answer 1

The phrase 5' to 3' denotes the direction DNA is synthesized by DNA polymerase, which begins at the 5th carbon of the deoxyribose sugar and extends to the 3rd, a key aspect of DNA replication. It applies to both the leading strand and the lagging strand, which is synthesized in Okazaki fragments.

Step-by-step explanation:

The descriptive phrase 5' to 3' refers to the direction in which DNA polymerase adds nucleotides during DNA replication. Specifically, it pertains to the arbitrary but understood numbering of the carbon atoms in the deoxyribose sugar of a DNA molecule. More precisely, this numbering system identifies the 5th and 3rd carbon atoms on the sugar molecule which are critical in the formation of the phosphodiester linkage during nucleotide polymerization. DNA polymerase can only synthesize DNA in the 5' to 3' direction, which applies to the leading strand synthesis towards the replication fork and the lagging strand synthesis away from the replication fork in the form of Okazaki fragments. The lagging strand is synthesized in short fragments since each Okazaki fragment starts with an RNA primer and is later joined by DNA ligase to form a continuous DNA strand.