Deoxiribonucleic Acid or DNA is the genetic material which carries the instructions for development and function for all living things. The main function of DNA is to store information in a lonegr period of time. (Campbell, Reece & Simon, 2006). DNA contains instructions that are necessary to constitute other cell components like proteins and ribonucleic acid (RNA). Genes are portions of DNA that helps maintain and regulate genetic information (Campbell, Reece & Simon, 2006). Deoxiribonucleic Acid is arranged on the chromosomes that are situated in the cell’s nucleus (Campbell, Reece & Simon, 2006).
Basically, the physical structure of DNA is comprised of a series of nucleotides or simple strands bound together like a chain (Caampbell, Reece & Simon, 2006). The chain of strands are arranged linearly in a structure similar to that of a spiral staircase which is called a double helix (Campbell, Reece & Simon, 2006). A nucleotide has three components; deoxiribose or sugar, phosphate groups and one of following: adenine, guanine, thymine and cytosine which are called bases (Campbell, Reece & Simon, 2006).
The deoxiribose is the center constituent bordered by a phosphate group on one side and one of the four bases on the other (Campbell, Reece & Simon, 2006). Each phosphate group of a nucleotide corresponds with the phosphate groups of other nucleotides within the chain (Campbell, Reece & Simon, 2006). The sequence of these four bases is bound with deoxiribose, this bonding of the three components are the perpetrators of the information encoded in the genes.
Chemically, a nucleotide on a DNA strand complements the nucleotide on the other strand. This is caused by the chemical affinity of the bases. These bases are conjoined by a weaker chemical bond called hydrogen bonds (Campbell, Reece & Simon, 2006).
Deoxiribonucleic Acid’s physical and chemical structure allows inheritance in a molecular level. The chemical affinity of the bases and the two-stranded nature of DNA causes redundancy between two complementing strands (Campbell, Reece & Simon, 2006). Therefore, the structure per se of the DNA is the ground for physical inheritance. Inheritance starts through the process of the DNA duplication . In the duplication process, the splitting DNA strands reciprocate the genetic information upon division and serves as a template for combination with a new partner strand. Genes are arranged in a parallel manner, in line with the chromosomes, with each cell having a single circular chromosome (Campbell, Reece & Simon, 2006).
The DNA of chromosomes are integrated with structural proteins forming a material called chromatin, with organized, compact and controlled access to the DNA itself. The combined DNA sequences of all chromosomes, called the genome, compose the full set of hereditary materials. Conversely, there is an exception on the structure of the sex chromosomes (Campbell, Reece & Simon, 2006).
In humans and other mammals there are very few genes in the Y chromosome which help develop male sexual characteristics (Campbell, Reece & Simon, 2006). The X chromosome on the other hand is in resemblance with other chromosomes which have genes that are not inclined to sexual identification. Each Male has a copy of the X and Y chromosome while females have two copies of X chromosomes, the difference in terms of the number of chromosomes lead to the peculiar inheritance patterns surrounding gender oriented disorders (Campbell, Reece & Simon, 2006).
In a normal account, DNA replication happens before cell division. During meiosis, particularly in animals, the result of such cell division produces the gamete cell. In this process, the number of germ cells are divided, therefore, the the DNA is divided in terms of the the number of sets of chromosomes, from two to one (Campbell, Reece & Simon, 2006).
In its most essential context, inheritance occurs through the distinct characteristics of the genes. Gregor Mendel was the first to have observed such phenomenon in his study of heritable properties on pea plants (Campbell, Reece & Simon, 2006). In the course of studying flower color, Mendel discovered that the color of the flowers for each pea plant were only limited to either purple or white, no other color or shade came in between. The unique versions of the 2 similar genes were dubbed as alleles (Campbell, Reece & Simon, 2006).
In Mendel’s observation, each gene has two alleles in an organism, the plants inherit each gene from the two parents. It was discovered in Mendel’s observation that it also apply to human genes. The raionale of Mendel’s patterns of inheritance are found on the nucleus of the cell. The components of the cell nucleus are chromosomes that carry genetic traits which are inherited upon cell division and reproduction (Campbell, Reece & Simon, 2006).
The products of cell division are called chromatids, these chromatids are the identical copies of the DNA. The subsequent product, the gamete cell has only one gene allowing maternal and paternal alleles in the offspring. In reproduction, the union between the male and female cells forms a full set of chromosome, in this sense the original composition is restored when the two genes are mixed (Campbell, Reece & Simon, 2006). The offspring then signifies that there is a connection between DNA replication and Mendel’s principles on the patterns of inheritance (Campbell, Reece & Simon, 2006).
Campbell, N.A, Reece, J.B, & Simon, E.J. (2006). Essential Biology with Physiology 2nd Edition. New York: Benjamin Cummings Publishing Company.