Discuss the Role of Enzymes in Dna Replication Essays

Discuss the Role of Enzymes in Dna Replication Essays Discuss the Role of Enzymes in Dna Replication Essay Discuss the Role of Enzymes in Dna Replication Essay DNA is the key for our genetic apperance. DNA is a double stranded and is formed by blocks of nucleotides. Nucleotides each consist of three parts. A phosphate, a pentose sugar (deoxyribose) and a nitrogenous base. The nitrogenous bases carry the information for proteins which are needed in our body to function properly. Proteins are made according to the nitrogenous bases. When DNA replicates, its extremely important that it is copied exactly. If its not the protein which is produced according to the nitrogenous bases. DNA replication process starts with unzipping the original strands by breaking the hydrogen bonds between base pairs which are connected according to a certain rule. Adenine bonds with two hydrogen bonds to Thymine, while Guanine bonds with three hydrogen bonds to Cytosine. Double ringed nucleotide bases are Adenine and Guanine which are called Purines, and single ringed nucleotide bases are Pyrimidines that consist of Thymine, Cytosine and Uracil. During the process of helicase breaking the hydrogen bonds between the two strands of the double helix structure of DNA where it forms a replication fork, Gyrase releases the tension in the strands by relieving twist at swivel points. The enzyme RNA polymerase (or primase) makes a piece of a RNA which is called a primer) against to the exposed DNA. Then DNA polymerase causes free nucleotides (from digested food) to bond to the exposed DNA bases adjacent to the primer and so form a new side of DNA called the leading strand. Nucleotides can only be added to the 3 end so on the leading strand they can be added one at the time. DNA polymerase always reads along the parental strand in a 3 to 5 direction , therefore the new DNA strand grows in a 5 to 3 direction. Two strands of the DNA have different beginnings and endings, thus its structure called anti-parallel. The other original strand, running 5 to 3, must be copied in short fragments (Okazaki fragments of approximately 1000 bases) and is called the lagging strand. DNA polymerase cant begin a new DNA strand from 5, therefore RNA polymerase (or primase) needs to make several primers (pieces of RNA). RNA polymerase replaces Thymine with Uracile, but Uracile is not acceptable in a DNA strand. Therefore it needs to be replaced. DNA polymerase replaces the piece of RNA primer with DNA nucleotides. This happens in both the leading and lagging strands. The new nucleotides and Okazaki fragments are joined into a strand of DNA by ligase and the process is called ligation. As a result two identical strands of DNA are produced. The process of DNA replication is semi-conservative because one side of the replicated DNA is new while the other half is original DNA.