Question

During replication, DNA dependent RNA polymerase works in direction _{_________} and from Okazaki, the polarity of other parental strand is _{________}.

Answer 1

RNA polymerase moves from the 3′ end of the template strand, creating an RNA strand that grows in a 5′ → 3′ direction (because it must be antiparallel to the template strand).

Okazaki fragments are short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication. They are complementary to the lagging template strand, together forming short double-stranded DNA sections

On the leading strand DNA replication proceeds continuously along the DNA molecule as the parent double-stranded DNA is unwound, but on the lagging strand the new DNA is made in installments, which are later joined together by a DNA ligase enzyme. This is because the enzymes that synthesize the new DNA can only work in one direction along the parent DNA molecule and the two strands are anti-parallel. On the leading strand this route is continuous, but on the lagging strand it is discontinuous.

DNA is synthesised from 5' to 3', so when copying the 3' to 5' strand, replication is continuous. Phosphodiester links form between the 3' to 5' and nucleotides can be added with the aid of the enzyme DNA polymerase for the continuous leading strand. However, in order to synthesise the lagging strand (the 3' to 5' strand) synthesis must occur in small sections (100-200 nucleotides at a time in eukaryotes). These new stretches of DNA are called Okazaki fragments and each one requires its own RNA primer.