Question
The correct sequence of enzymes required for DNA formation is:
A. DNA polymerase Protein unwinding enzyme –> DNA ligase –> DNA Isomerase –> Polymerase -1
B. Protein unwinding enzyme –> Polymerase 1 –> DNA ligase–> DNA Isomerase–> DNA
C. RNA polymerase –> DNA polymerase III –> DNA polymerase I –> DNA ligase
D. RNA polymerase –> DNA polymerase III –> DNA ligase –> Exonuclease DNA polymerase I
Show Answer
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Correct Answer » C
Explanation
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Origin of Replication- The DNA replication starts with the recognition of the site of origin of replication. This is done by a complex called autonomous replicating sequences.
The unwinding of DNA– Topo-isomerases, Gyrases, and Helicases, all of them unwind the DNA.
Components of DNA Replisome-DNA replication need the participation of more than 20 enzymes and proteins collectively called replisomes.
DNA Polymerase (DNAP)– In mammalian cells (eukaryotic), there are 5 DNAPs, named as α, β, γ, δ, ε. The enzyme polymerase alpha is the major enzyme responsible for chromosome replication.
Bacterial DNA polymerases-
RNA Primer is Required for DNA Synthesis- An RNA primer is synthesized by the RNA primase. Then the RNA primer is removed by DNAP, using exonuclease activity and is replaced with deoxyribonucleotides by DNAP
Elongation of DNA Strand- The extension of nucleotide primers requires a group of enzymes called DNA polymerases. Escherichia coli contains DNA polymerases I, II, and III, polymerase III being important for DNA the de novo synthesis of new DNA strands and polymerase I for editing out unpaired strands at the end of the growing strand The base-pairing rule is always observed.
Discontinuous Synthesis and Okazaki Pieces- DNA synthesis is discontinuous in the lagging strand (away from the fork), as Okazaki fragments. The remaining nick is sealed by the DNA ligase.
Condensation into Chromatin Structure- Proofreading is done by DNA polymerase. Finally organized into chromatin.
