DNA mutagen and DNA mutation - The Veterinary Site

DNA mutagen and DNA mutation

Today we are scientific era as this era remover the facts of many hidden things and produce essence for mankind but the dark aspects of this era are that as it is producing facilities for mankind on the other hand it producing harmful things that are deteriorating our life. One of these effects is on our DNA material in our cell. Environment has become polluted to such an extent that in the coming next day’s survival of life will become difficult. Radiations, chemicals and other harmful effects are causing the change in our DNA material due to these changes in genomic material different diseases are produced and these days’ incurable.
It is a change in the base sequence of DNA. Such change in the base sequence of a gene will some time cause a change in the product encoded by that gene e.g.  When a gene for an enzyme mutates the enzyme encoded by the gene may become inactive or less active because its amino acid sequence has changed.

Types of mutation

Following are the types of mutation
·         Base Substitution or Point Mutation
·         Frame Shift Mutation
Base Substitution or Point Mutation
At one point a single base is replaced in DNA sequence by a different base. When this DNA replicates it results in substituted base pairing. It has two types.
1.       Missense Mutation
If a base substitution results in amino acid substitution in the synthesized protein, this change is known as missense mutation. The effect of such kind of mutation can be dramatic e.g. sickle cell disease is caused by a single change in the gene of globin which is a protein component of hemoglobin.  A change from A to T at a specific site results in change from glutamic acid to valine in the protein. The effect is that the shape of the hemoglobin molecule changes under low O2 altering the shape of the RBCs such that the movement of cell though the small capillaries is greatly impeded.
2.       Non-sense Mutation:
If base substitution results in the creation of nonsense or stop codon in the middle of mRNA molecules thus it stops protein synthesis. This type of base substitution is known as nonsense mutation.
Frame Shift Mutation
If one or few nucleotides are deleted or inserted in the DNA then it can shift the translation reading frame e.g. deleting one nucleotide pair in the middle of a gene cause change in many amino acids downstream from the site of mutation. Frame shift mutation always result in a long stretch of altered protein or amino acid and the production of an inactive protein from a mutated gene.
Agents in the environment such as certain chemicals and radiations which directly bring about mutation are called mutagens. Mutagens are of different types i.e. chemical mutagens, radiations etc.
·         Chemical Mutagens
One of the many chemicals known to be mutagen is Nitrous acid. Exposure of DNA to nitrous acid can convert the base adenine to a form that no longer pairs with instead it pairs with cytosine. When DNA containing such modified adenine replicates one daughter DNA molecule will have base pair sequence different from that of parent DNA eventually some AT base pairs of parent will have been changed to GC base pair in the grand daughter cells. Nitrous acid makes a specific base pair change in DNA like all mutagens it alters DNA at random locations.
·         Nucleoside Analogue
Another type of chemical mutagen is nucleoside analogue. These molecules are structurally similar to normal nitrogenous base but they have slightly altered base paring property. For example, 2-amino protein and 5-bromouracil are analogue to adenine and thymine nucleotide respectively. Aflatoxins produced by Aspergillus flavors is a frame shift mutagen
·         Radiations
 x-rays and gamma rays are form of potent mutagens because of their ability to ionize atoms and molecules the penetrating rays of ionizing radiations cause electrons to pop out of their usual cells. These electrons bombard other molecules and cause more damage. Many of the resulting ions and free radicals are very reactive. Another form of mutagenic radiations is UV light a non-ionizing component of ordinary sunlight. The most important effect of direct UV light on DNA is the formation of harmful covalent bond between certain bases adjacent T(Thymine) in DNA strand can cross link to form T dimers unless repaired may cause serious damage or death to the cell because it cannot properly transcribe or replicate such DNA.
Effects of Mutagens
Mutagens effect the genomic material therefor they are also called as genotoxic. These effects all the normal processes occurring in the normal cell i.e. Transcription and Translation, Replication of DNA etc. Sometime these mutagens stop these processes or sometime these processes run at uncontrolled rate. Mutagens cause addition, deletion, Insertion of new gene that cause many genomic problems sometime even a single base pair change can cause deleterious effect. These mutagens cause the rapid proliferation of cell and cause cancer. As genomic information is converted into protein synthesis these mutagens cause the change in DNA sequence and the resulting proteins are defective i.e. Enzymes produced in storage disease are defective and in Hemophilia RBC’s are unable to carry oxygen due to mutation in gene
Sources of Mutagens
In our daily life we come across many substances that are causing mutation these things include i.e.
·         Free radicles produced in our body
·         Continuous exposure of x-rays
·         UV light present in atmosphere
·         Harmful rays from volcanic eruption
·         Harmful rays from explosive material
·         harmful Industrial waste i.e. Cobalt-60, Cesium-137 etc.
·         Aromatic amines
·          Alkaloids
·         Heavy metals
·         Bromines etc.
Protection Against Mutagens
Nature has made Anti-oxidant system in our body to combat against free radicles produced in our body we also take anti-oxidant i.e. vitamin A, carotenoids, vitamin C etc. from different various vegetables, fruits etc.  Selenium which is present as a micronutrient in vegetables, is a component of important antioxidant enzymes such as glutathione peroxidase.
An effective precautionary measure for an individual is that he should protect himself from continuous exposure of X-rays or other harmful radiations and should take effective measure to control them. He should avoid certain chemicals that are causing health damage i.e. industrial waste contain many radioactive isotopes that are continuously emitting rays. These rays are also produced from atomic bomb explosion one of the best examples are the atomic explosion on two cities of Japan in world war II effect of these radiations ids still present therefore explosive material should be banned.
Radiation and other harmful chemicals are the cause of many diseases therefore we should take effective steps to control them otherwise it will reach to such an extent that it will be out of control. Ozone layer is finishing day by day which is also causing many skin and other problems. Use of radioactive substances should be banned and if they are used these substances must be disposed of properly by applying proper techniques.
We can also save us from these mutagens by arranging seminars on the control of these mutagens.

Submitted by
Dr Usman khalid
M Arslan 
Usama arshad
DNA mutagen and DNA mutation DNA mutagen and DNA mutation Reviewed by Maaz ahmed siddiqui on 15 May Rating: 5

1 comment:

  1. please add download option to download article in pdf/ word format.....


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