DNA: Watson & Crick perspective

Deoxyribonucleic acid (DNA) is a molecule that carries the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. DNA and RNA are nucleic acids; alongside proteins, lipids and complex carbohydrates (polysaccharides), they are one of the four major types of macromolecules that are essential for all known forms of life. Most DNA molecules consist of two biopolymer strands coiled around each other to form a double helix. DNA stores biological information. This information is replicated as and when the two strands separate. A large part of DNA (more than 98% for humans) is non-coding, meaning that these sections do not serve as patterns for protein sequences.

Double Helix structure of DNA

• Chargaff's realization that A = T and C = G, combined with some crucially important X-ray crystallography work by English researchers Rosalind Franklin and Maurice Wilkins, contributed to Watson and Crick's derivation of the three-dimensional, double-helical model for the

structure of DNA. DNA is a double-stranded helix, with the two strands connected by hydrogen bonds. A bases are always paired with Ts, and Cs are always paired with Gs, which is consistent with and accounts for Chargaff's rule.

• Most DNA double helices are right-handed; that is, if you were to hold your right hand out, with your thumb pointed up and your fingers curled around your thumb, your thumb would represent the axis of the helix and your fingers would represent the sugar-phosphate backbone. Only one type of DNA, called Z-DNA, is left-handed.

• The DNA double helix is anti-parallel, which means that the 5' end of one strand is paired with the 3' end of its complementary strand (and vice versa). As shown in Figure 4, nucleotides are linked to each other by their phosphate groups, which bind the 3' end of one sugar to the 5' end of the next sugar.

Nutrigenomics

Nutrigenomics is a branch of nutritional genomics and is the study of the effects of foods and food constituents on gene expression. This means that nutrigenomics is research focusing on identifying and understanding molecular-level interaction between nutrients and other dietary bioactives with the genome. The interaction between genetic and dietary influences can result in a higher risk of disease in certain individuals and populations. Currently, diet-gene association studies are revealing evidence on which to base gene-specific dietary intervention trials to confirm results. By determining the mechanism of the effects of nutrients or the effects of a nutritional regime, nutrigenomics tries to define the causality or relationship between these specific nutrients and specific

nutrient regimes (diets) on human health. Nutrigenomics has been associated with the idea of personalized nutrition based on genotype. While there is hope that nutrigenomics will ultimately enable such personalised dietary advice, it is a science still in its infancy and its contribution to public health over the next decade is thought to be major. Whilst nutrigenomics is aimed at developing an understanding of how the whole body responds to a food viasystems biology, research into the effect of a single gene/single food compound relationships is known as nutrigenetics. Aging of cells occur because of the accumulation of excess free radicals formed due to the lack of proper nutrition to the cells and external factors like UV rays, pollution, stress, food, etc. DNA analysis is instrumental in identifying the right concoction of nutrients needed to eliminate the excess free radicals present in the cell. Obesity is one of the most widely studied topics in nutrigenomics. Due to genetic variations among individuals, each person could respond to diet differently. By exploring the interaction between dietary pattern and genetic factors, nutrigenomics aim to suggest prevention measures and/ or treatment to obesity via personal nutrition. To put nutrigenomics into practice, genetic testing is required as the test results act as the reference for diagnosis. As the subject is recently commercialized by companies which sell direct to customer (DTC) genetic tests, as well as being applied by related professionals (such as dietic practitioners), there have been increased awareness in the use of this information. These concerns include but are not limited to the lack of analytical and clinical validity of genetic tests, emotional distress of consumers, and other social concerns.One of the major concerns regarding genetic tests would be privacy issue. There are concerns on who has the right to have access to test results. Abuse of these tests could result in discrimination. For example, genetic information might be used by insurance companies to risk rate their clients. One of the possible ethical concerns arise would be private companies providing unverified information regarding test results. Interpretations on genetic test results needs to be handled very carefully Misleading and/or inaccurate information may as well undermine customers' ability to make informed decisions. Misinterpretation could possibly mislead patients and hence false medical claims are made. Refrences

1. Watson, J. D., & Crick, F. H. C. A structure for deoxyribose nucleic acid. Nature 171, 737–738 (1953).

2. In Dube L, Bechara A, Dagher A, Drewnowski A, LeBel J, James P, Yada RY & Laflamme-Sanders M-C. Obesity Prevention: the role of society and brain on individual behavior. pp. 149-160.

3. Müller M, Kersten S. (2003). Nutrigenomics: goals and strategies. Nature Reviews Genetics. 4(4): 315-322.

4. Castle, David; Ries, Nola M. (2007-09-01). "Ethical, legal and social issues in nutrigenomics: The challenges of regulating service delivery and building health professional capacity". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis. Nutrigenomics. 622 (1–2): 138–143.

Presented By :- NISHA (20863) ANIL KUMAR (20835) BALWANT SINGH (20836)