DNA SEQUENCING TECHNIQUES

DNA Sequencing Techniques



DNA Sequencing Techniques

Introduction

DNA is the abbreviation for the double helix molecule, deoxyribonucleic acid. It is a long chain polymer (polynucleotide) which is found is all living cells. Using its chemical patterns it directs the formation, growth, operations and reproduction of individual cells and thus of organs and of living organisms. The DNA molecule is very long and is like a spiral staircase or a double helix in structure. The structure of DNA was first discovered by James D. Watson and Francis H. C. Cricket in 1953. The discovered of the structure opened the way for detailed understanding of the chemistry of the DNA molecule and of genetics as well.

DNA molecules are composed of two polynucleotide strands wrapped around each other to form a double helix. They consist of two long nucleotides composed of a sugar molecule and a phosphate group bonded to a DNA base. This sequence is repeated numerous times to form genes and chromosomes. The legs of the DNA spiral staircase have major and minor groves. Other chemicals form the connecting steps. The whole molecule is composed of thousands of smaller chemical units called nucleotides which are bonded together to form polynucleotides.

A gene is a segment of DNA that carries the information needed by the cell to construct a protein. Which protein that is, when it is made, and how damage to it can give rise to genetic disease all depend on the gene's sequence. In other words, they depend on how the building blocks of DNA, the nucleotides A, C, G, and T (adenine, cytosine, guanine, and thymine) are ordered along the DNA strand. For example, part of a gene may contain the base sequence TGGCAC, while part of another gene may contain the base sequence TCACGG. Knowing a gene's base sequence can lead to isolation of its protein product, show how individuals are related, or point the way to a cure for those people carrying it in its damaged form (Bloom, et al., 2005).

DNA Sequencing Techniques: An Overview

In DNA replication a common mutation occurs with two thymines or a cytosine are exposed to ultraviolet (UV) light. The UV light causes thymine dimmers to form. This causes pattern disorder in the DNA molecule and blocks its normal functioning.

The DNA base cytosine was first discovered in 1894. It is a phyimidine derivative with a heterocyclic aromatic ring. Isolated from the thymus tissue of a calf it was within 10 years synthesized in laboratory experiments. Its atomic structure was understood by 1903. It is one of the nucleotide bases of DNA. It has a key role in genetic information transmission. Cytosine bonds with guanine with three hydrogen atoms.

DNA has the ability to transmit genetic information that is needed by living cells to reproduce. This ability is closely related to the structure of DNA. While DNA is a polymer it is composed of long chain monomer (nucleotides). In each nucleotide is a sugar, a nitrogen molecule in the form of a molecular ring (base) and a ...