DNA Replication in Eukaryotes

DNA replication in eukaryotes is semiconservative where each strand in the double helix splices synthesizing a new complementary strand. DNA polymerases are the enzymes responsible for synthesizing new DNA in the replicated strands (Devbhandari et al.). They require a platform and a primer to produce DNA. A chiseled set of DNA polymerases each individually adapted for a particular pathway are mostly produced. However, cross-functionality in some DNA polymerases having different pathways. DNA polymerase alpha is needed for the commencement of DNA replication.

             DNA polymerases add nucleotides sequentially developing a DNA chain. They can only grow a pre-existing chain known as a primer unable to make a new DNA chain. DNA polymerase assesses their work correcting all unsuitable nucleotides through disposal. DNA polymerases locate a specific point on the DNA known as origins of replication distinguished by their sequence (Maric et al.). Specialized proteins find the origin and attach making a pore to expose the DNA, two Y-shaped components called replication forks are developed, merging together forming a replication bubble.

            These forks will spread in the opposite direction as the replication continues. Helicase is the first enzyme to actuate the replication forks through detaching nitrogenous base pairs through the breaking of hydrogen bonds while moving unidirectionally between the duplex helix at the origin of replication (Stillman). The synthesized strands grow in opposite direction where the leading one is produced in the direction towards the replication fork where helicase enzyme unwinds the template double-stranded DNA and the lagging strand is produced in the direction away from replication fork and helicase activity. The lagging strand synthesizes in bits known as Okazaki fragments each commencing with its own RNA primer.

Works Cited

Devbhandari, Sujan, et al. "Chromatin constrains the initiation and elongation of DNA            replication." Molecular cell, vol. 65, no. 1, 2017, pp. 131-141.

Maric, Marija, et al. "Cdc48 and a ubiquitin ligase drive disassembly of the CMG helicase at the end of DNA replication." Science, vol. 346, no. 6208, 2014.

Stillman, Bruce. "Reconsidering DNA polymerases at the replication fork in            eukaryotes." Molecular cell, vol. 59, no. 2, 2015, pp. 139-141.