Essay on Replication

Essay by Dusk2k2High School, 11th grade April 2004

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Essay on Replication

Replication occurs during the S Phase of the cell cycle. Initiator proteins begin the process. The strands are separated by the enzyme helicase. DNA polymerase begins replicating the leading strand in the 5' to 3' direction since DNA is antiparallel. The other strand, or the lagging strand, uses primase to copy the strand in the 5' to 3' direction but it only does a few nucleotides at a time. These fragments are called Okazaki fragments and they are ligated by an enzyme called ligase. Topoisomerases are enzymes that keep the opening helixes from kinking when unwound. Single-strand binding proteins are used to help the polymerases code for the right nucleotides and keep the process going smoothly. DNA polymerase later proofs its work afterwards and repair enzymes replace wrongly placed nucleotides. This prevents mutations in DNA.

DNA cannot begin the strand so RNA primase is used to do about the first ten nucleotides.

This beginning is called a primer and is later replaced with DNA molecules. The single-strand-binding proteins also help keep the strands apart. Nuclease cuts out the bad nucleotides. Telomeres are the sequences at the end of the strands that do not particularly code for anything but the shorter they get the less likely it is that that cell will reproduce.