rolling circle model of dna replication
rolling circle model of dna replication
Answered
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Initiation of Replication
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The process begins when an initiator protein binds to the origin of replication on the circular DNA molecule.
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This protein introduces a single-strand nick at a specific site, creating a 3′ hydroxyl group and a 5′ phosphate group.
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The 3′ end serves as a primer for DNA synthesis, while the 5′ end is displaced and remains bound to the initiator protein.
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Elongation of the Leading Strand
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DNA polymerase III attaches to the 3′ end of the nicked strand and begins synthesizing the new DNA strand in the 5′ to 3′ direction.
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The original, uncut strand acts as the template for this continuous synthesis.
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As replication progresses, the newly synthesized strand displaces the original strand, forming a single-stranded DNA (ssDNA) molecule.
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Formation of Concatemers
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The continuous replication around the circular DNA template results in the production of concatemeric DNA.
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A concatemer is a long, linear DNA molecule consisting of multiple linked copies of the original genome.
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These concatemers can be several kilobases in length and are often cleaved into unit-length genomes for packaging into new virions.
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Termination and Circularization
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Replication continues until a termination signal is encountered, at which point the initiator protein makes another nick to release the newly synthesized strand.
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The free 3′ end of the released strand serves as a primer for the synthesis of a complementary strand, converting the ssDNA into double-stranded DNA (dsDNA).
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DNA polymerase I removes any RNA primers, replacing them with DNA nucleotides, and DNA ligase seals the nicks, resulting in a complete circular dsDNA molecule.
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Check this note –
Rolling Circle Replication – Mechanism, Application
BNO Team
