Dna Structure

DNA, which stands for Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms. The main role of DNA molecules is the long-term storage of information. These nucleic acids consist of long chains if chemical units called nucleotides. Nucleic acids are information storage molecules that provide the directions for building proteins. Described by the DNA testing centre, Inc., “DNA is found inside the chromosome, inside the nucleic of the cell. Each chromosome is made up of a tightly coiled strand, a molecule of DNA. The bases in the opposite strands are arranged such that where there is an adenine (A) in one strand, the other strand has a thymine (T) and where there is a guanine (G) in one strand, the other strand has a cytosine (C).” (The DNA Testing Centre, Inc., 2007). Each strand is made up of a sugar covalently linked to a phosphate which is covalently linked to another sugar and so on. A DNA strand may contain thousands to millions of these sugar-phosphate units. Each strand of DNA is formed by units of phosphate (P) joined with units of deoxyribose (D). These units alternate to make the bases of a strand of DNA. The two side strands are connected by the two bases. The four possible pairs are A-T and G-C.

When a cell or a whole organism reproduces, a complete set of genetic instructions must pass from one generation to the next. “The two strands of the original DNA molecule serve as templates for new strands. DNA replication result in two daughter molecules, each consisting of one old strand and one new strand. The parental DNA untwisted as its strands separate, and the daughter DAN rewinds as it forms.” (Essential biology and physiology, chapter 10, P.179). This whole process called DNA replication. There is flow of genetic information from DNA to RNA to protein, which is divided in two stages, transcription and translation. A sequence of nucleotides in the DNA is transcribed into a molecule of RNA in the cell. The RNA travels to the cytoplasm, where it is translated into the specific amino acids sequence of a protein.

According to DNA roots (2007) “DNA is responsible for the transmission of characteristics us inherit from our parents. Every individual is made from cells containing DNA in the cell nuclei. DNA is comprised of 23 pairs of chromosomes, and each of these contains genetic sequences. We inherit half of our chromosomes from our mother and half from our father.” (DNA roots, 2007). Every individual in this world have different DNA from another, expect for identical twins.

Meiosis is the process of cell division in sexually reproducing organisms that reduces the number of chromosomes in reproductive cells from diploid to haploid, leading to the production of gametes in animals and spores in plants. “As the cell begins meiosis, each chromosome has already duplicated its deoxyribonucleic acid (DNA) and carries two identical copies of the DNA molecule. These are visible as two lateral parts, called sister chromatids, which are connected by a Centromere. Homologous pairs of chromosomes are first identified and matched.” (Peter S., DNA diagnostics center, 2007). This process, which occurs only in the first of the two meiotic divisions, is called pairing. The matched pairs are then physically interlocked by recombination, which is also