DNA (Deoxyribonucleic Acid)

Deoxyribonucleic Acid (DNA) is genetic material found in the cells of all living organisms. DNA is the fundamental building blocks for life. Nearly every cell (with a nucleus) in a person's body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but DNA can also found in the mitochondria (where it is called mitochondrial DNA or mtDNA).The information in DNA is made up four bases which combine to form chains. These bases include two purines (Adenine and Guanine) and two pyrimidines (Cytosine and Thymine). These are commonly referred to as A, G, C and T respectively. Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. It is the order, or sequence, of these bases which determines genetic characteristics.

The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder's rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder. Each base is attached to a Sugar (S) molecule and Phosphate (P) molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. The number of purine bases in DNA is equal to the number of pyrimidines. This is due to the law of complimentary base pairing. which is Thymine (T) can only pair with Adenine (A), and Guanine (G) can only pair with Cytosine (C). Knowing this rule, we could predict the base sequence of one DNA strand if we knew the sequence of bases in the complimentary strand.

DNA is Double Helix

DNA is shown in the double-stranded helical model for the graphic on the left. The easiest way to visualize DNA is an immensely long rope ladder, twisted into a cork-screw shape. The sides of the ladder are alternating sequences of deoxyribose and phosphate (backbone) while the rungs of the ladder (bases) are made in two parts with each part firmly attached to the side of the ladder. The parts in the rung are heterocyclic amines held in position by hydrogen bonding. Although most DNA exists as open ended double helices, some bacterial DNA has been found a cyclic helix. Occasionally, DNA has been found as a single strand.

Forensic DNA Testing

There are two main types of forensic DNA testing. Called, RFLP and PCR based testing, although these terms are not very descriptive. Generally, RFLP testing requires larger amounts of DNA and DNA must be underrated. Crime-scene evidence that is old or that is present in small amounts is often unsuitable for RFLP test. Warm moist conditions may accelerate DNA degradation rendering it unsuitable for RFLP in relatively short period of time.

PCR-based testing often requires less DNA than RFLP testing and the DNA may be partially degraded, more so than is the case with RFLP. However, PCR still has sample size and degradation limitations that sometimes may under-appreciated. PCR-based tests are extremely sensitive to contaminating DNA at the crime scene and within the test laboratory. During PCR, contaminants amplified up to a billion times their original concentration. Contamination can influence PCR results, particularly in the absence of proper handling techniques and proper controls for contamination.PCR are less direct and more prone to error than RFLP. However, PCR has tended to replace RFLP in forensic testing primarily because PCR based tests is faster and more sensitive.

DNA Analysis and Gene Cloning

Known world wide as the standard introductory test to this important and exciting area, the fifth edition of Gene Cloning and DNA Analysis addresses new and growing area of research which retaining the philosophy of the previous edition. Assuming the reader has little prior knowledge of subject is important. The principles of the techniques used and their applications are all carefully laid out. With over 250 clearly presented two color illustrations.

In addition to number of informative changes to the test throughout the book, The final four chapters have been significantly updated and extended to reflect the striking advances made in resent years in the application of gene cloning and DNA analysis in biotechnology.

Extended chapter on agriculture including new material on glyphosate resistant plants, New section of the uses of gene cloning and PCR in archaeology. Coverage of ethical concerns relating to farming, Gene therapy and GM crops, Gen Cloning and DNA Analysis remains and essential industry test to wide range of biological science Students including genetics and genomic, molecular biology, biochemistry, immunology and applied biology. It is perfect industry test for any processional needing to learn to basic of the subjects. All libraries in universalities where medical, life and biological sciences are taught should have copies available their shelves.

MICROARRAYS Applications

DNA Microarray technology helps in the identification of new genes, know about their functioning and expression levels under different conditions. Disease diagnosis:- DNA Microarray technology helps researchers learn more about different diseases such as heart diseases, mental illness, infectious disease and especially the study of cancer. Until recently, different types of cancer have been classified on the basis of the organs in which the tumors develop. Now, with the evolution of microarray technology, it will be possible for the researchers to further classify the types of cancer on the basis of the patterns of gene activity in tumor cells. This will tremendously help the pharmaceutical community to develop more effective drugs as the treatment strategies will be targeted directly to the specific type of cancer.

Drug discovery:- Microarray technology has extensive application in Pharmacogenomics. Pharmacogenomics is the study of correlations between therapeutic responses to drugs and the genetic profiles of the patients. Comparative analysis of the genes from a diseased and normal cell will help the identification of the biochemical constitution of the proteins synthesized by the diseased genes. The researchers can use this information to synthesize drugs which combat with these proteins and reduce their effect.

Toxicological research:- Microarray technology provides a robust platform for the research of the impact of toxins on the cells and their passing on to the progeny. Toxicogenomics establishes correlation between responses to toxicants and changes in the genetic profiles of the cells exposed to such toxicants.

RNA Data Sequences in DNA

Proteins are not the only substances that are synthesized directly from data within the DNA. Some forms of RNA are specialized, and also have their formula encoded directly in digital DNA formulae. Not all types of RNA are temporary intermediate forms with their form depending on whatever DNA they are copying. There are certain forms of RNA that have a particular form that is the same across all individuals. Some of these special-purpose RNA forms are,
1. tRNA - transfer RNA
2. rRNA - ribosome RNA

There are exactly 20 forms of tRNA, one each transfer a particular amino acid. tRNA molecules contain about 75-80 bases. tRNA recognizes one of the 64 triplets, and matches it one of the 20 amino acids. Since there are 20 tRNA types, and not 64, each tRNA molecule has to recognize more than one triplet ordering as a match. The DNA code contains multiple repetitions of codes for tRNA and rRNA. About 280 copies are spread over 5 chromosomes. Presumably, this allows each cell to make multiple copies of tRNA and rRNA molecules at once from its single copy of the DNA.