How chromosome ends are replicated?

DNA replication is carried out by DNA polymerase. During the replication, one DNA strand synthesized as leading strand and the other as lagging strand. The leading strand synthesis is continuous, whereas lagging strand synthesis is discontinuous. DNA replication at the DNA ends i.e. telomeres is an altogether different story. If a primer forms at the [...]

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DNA polymerase III

DNA pol III is the principal replication enzyme of E. coli. The enzyme is highly complex and has more than 10 types of subunits. These subunits are α, ε, θ, τ, δ, δ’, β, χ, ψ, γ. The α, ε and θ subunits combine to form the core polymerase. The core polymerase has a limited [...]

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Why DNA pol I is not suited to replicate E. coli chromosome?

As mentioned earlier, DNA pol III is the enzyme which carries out the replication of large E. coli chromosome. DNA pol I, because of the following properties, does not qualify as the enzyme for E. coli chromosome replication:
1) The polymerization rate (nucleotides added/sec) of this enzyme is 16-20 nucleotides/sec or approximately 600 nucleotides/min, which [...]

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DNA polymerases of E. coli

DNA pol I: It is a single subunit enzyme with a mol wt of 103,000. It has 3′→5′ exonuclease proofreading activity. The polymerization rate, i.e. nucleotides added per second to a growing DNA molecule, is 16-20. The processivity of DNA pol I is 3-200. Processivity is the number of nucleotides before polymerase dissociates from [...]

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DNA Polymerases

The enzyme required for DNA replication is DNA polymerase. All living organisms which have DNA as their genetic material require DNA polymerase enzyme.
We will begin our discussion of DNA polymerases with the E. coli enzymes. This prokaryote has 5 different kinds of DNA polymerase: DNA pol I, DNA pol II, DNA pol III, DNA pol [...]

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Arthur Kornberg, discoverer of DNA polymerase, dies at 89

This post is a tribute to Arthur Kornberg. He died of respiratory failure on Friday in Stanford, California at the age of 89. He discovered the enzyme DNA polymerase, which replicates the DNA molecule. The search for an enzyme that could synthesize DNA started in 1955, which finally culminated in 1959 with a Nobel Prize [...]

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