Saturday, May 06, 2006


The DNA (Deoxyribonucleic acid) is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. It is regularly in the form of a double helix that has the genetic instructions specifying the biological development (the study of the process by which organisms grow and develop) of all the cellular forms of live and bacteria. It is very long molecule consisting of structural unit of nucleotides and encodes the sequence of the amino acid residues in protein using the genetic code, a triplet code of nucleotides.

The DNA is often called the molecule of heredity, because of its responsibility to genetic propagation of most inherited traits. It is replicated and can be transmitted to offspring during reproduction in the process of cell division. The DNA is a pair of molecules joined by the hydrogen bond. Every DNA strand is a chain of chemical ‘building blocks.’ There are about four types of nucleotides namely: (A) Adenine, (C) Cytosine, (G) Guanine and (T) Thymine. A is paired with T while G with C, that is A+T, T+A, C+G, G+C are possible combination and A+T is not the same as T+A as well as C+G is not the same as G+C.

The DNA contains the hereditary information that is inherited by the offspring of an organism; this information is determined by the sequence of base pair along its length. The DNA strand has genes, area that regulate genes and area that regulate genes and areas that either function are yet unknown or the does not have function.

The DNA is found throughout the body in cells, within cells in chromosomes and within each chromosome in genes. The body is formed from between 50 and 100 trillion cells. These cells are organised into tissues, such as skin, muscle and bone. Humans have two sets of 23 chromosomes in every cell, the Y chromosome and the X chromosome, the Y is for male and X for female therefore a human cell contains 46 of these chromosomal DNA molecules.

The DNA helps in identifying people. We use the DNA tests to find out about our relatives, families and also to trace the criminals. No matter how differently do we appear, in hair colours, facial structures, our movement, habits and other characters. This differences results from very little differences in their DNA sequences. The DNA of any two people on Earth is in fact, 99.9% identical. We inherit one copy from each parent, we have two copies. In order to understand fully our DNA sequences, both inherited copies of genes need to be carefully examined.

Using the DNA to trace a criminal, we compare the DNA data from the crime scene to the DNA profiles of the suspects using the CODIS sites, if the DNA samples match absolutely at the 13 regions used in the FBI’s CODIS system, then the probability that they come from two related people are 100%. This method helps in the identification of a relevant person for the scene.


1. Wikipedia contributors. DNA [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 3 10: 11 PTA Available from: [].

2. Wikipedia contributors. Gene [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 02, 10:00, PTA. Available from: [].

3. Wikipedia contributors. Nucleic acid [internet] Wikipedia, the free Encyclopaedia, 2006 May 03, 11; 30, PTA. Available from [].

4. Wikipedia contributors, biological development [internet]. Wikipedia, The Free Encyclopaedia, 2006 May 03, 12:50, PTA. Available from [].


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