DNA Replication in Prokaryotes Lecture Quiz

DNA Replication Overview

• DNA replication is essential for cell division, ensuring that each daughter cell receives an exact copy of the DNA.
• It is a semi-conservative process, meaning each new double helix contains one original strand and one newly synthesized strand.

Direction of Synthesis

• DNA polymerase synthesizes new strands in the 5' to 3' direction, adding nucleotides to the 3' end of the growing strand.

Role of DNA Helicase

• DNA helicase unwinds the double helix, separating the two strands to allow for replication to occur.

Requirement for RNA Primer

• DNA polymerases cannot initiate synthesis on a bare template strand; they require a short RNA primer to provide a starting point for DNA synthesis.

Function of DNA Ligase

• DNA ligase seals gaps between Okazaki fragments on the lagging strand, ensuring the continuity of the DNA molecule.

Semi-conservative Replication

• In semi-conservative replication, each parent strand serves as a template for a new complementary strand, resulting in two DNA molecules, each with one old and one new strand.

Enzyme for Supercoil Removal

• DNA topoisomerase is responsible for relieving the supercoiling tension that occurs ahead of the replication fork during DNA unwinding.

Function of DNA Topoisomerase I

• DNA topoisomerase I creates transient single-strand breaks in DNA to alleviate torsional strain generated during replication.

Enzyme for Progressive Unwinding

• DNA helicase actively unwinds the DNA double helix at the replication fork, allowing access for other enzymes involved in replication.

Role of Single-Strand Binding (SSB) Proteins

• SSB proteins stabilize unwound single strands of DNA, preventing them from re-annealing or forming secondary structures during replication.

RNA Primer Formation

• The enzyme primase synthesizes short RNA primers necessary for initiating DNA replication.

Function of DNA Polymerase III

• DNA polymerase III is the primary enzyme responsible for synthesizing new DNA strands during replication, working quickly and effectively on both leading and lagging strands.

Characteristics of DNA Polymerase III

• The high processivity of DNA polymerase III allows it to synthesize DNA at a rapid rate, making it efficient for replication.

Enzyme for Transient Breaks

• DNA topoisomerase II (or gyrase in bacteria) makes transient breaks in both strands of DNA, facilitating the untangling of DNA during replication.

Role of DnaA in Prokaryotes

• DnaA is involved in the initiation of DNA replication in prokaryotes by binding to the origin of replication, facilitating the unwinding of DNA.

Function of DNA Gyrase

• DNA gyrase is a type of topoisomerase that introduces negative supercoils into DNA, helping to relieve torsional strain in bacterial and plant DNA during replication.