Question

Use the following to answer the questions below: For each of the nucleic acid situations, select the process with which it is associated using the response list. Responses may be used more than once or need not be used at all. a) translation phase of protein synthesis b) transcription phase of protein synthesis c) replication of DNA d) post-transcription phase of protein synthesis Okazaki fragments are formed.

Answer 1

Option "C" is correct. Okazaki fragments are formed during the replication of DNA.

During the DNA replication , DNA polymerase III can add nucleotides only in 5' to 3' direction. (i.e. new nucleotides are added in 3' end only). As the two parent strands of DNA are antiparallel, the new strands are oriented in opposite directions. The new DNA strand synthesized on the parent template strand 3'-5' continuously grows, as 3'-OH is available to add the new nucleotide. This strand is formed first and so is called Leading strand. In contrast, the strand synthesized on parent strand 5'-3', is synthesized in small segments called Okazaki fragments which are later connected. This strand is called Lagging strand. The lagging strand, which elongates on the parent template (5' -3'), grows away from the replication fork. The Okazaki fragments are about 100 to 200 nucleotides long in eukaryotes and 1000 to 2000 nucleotide long in prokaryotes. Each Okazaki fragment is synthesized by DNA polymerase III in 5' to 3' direction. (on parent strand 3' - 5') When the polymerase reaches the 5' end of the lagging strand, an enzyme called DNA ligase, attaches the fragments. The DNA is further unwound, new RNA primer is constructed and DNA polymerase lll jumps ahead by 1000 to 2000 nucleotides towards the replication fork to begim uie construction of another Okazaki fragment. Because the synthesis of leading strand is continuous while that of the lagging strand discontinuous.