32 DNA Technologies and Medicine

Dr. Kanala Kodanda Reddy

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Content

· Introduction

· What is DNA Technology?

· Cloning

· Polymerase chain reaction (PCR)

· Recombinant DNA technology (Genetic engineering)

· Gene Therapy

· DNA microarray technology

· DNA profiling

· Application of DNA technology

· DNA technology in medicine

· Advantages of DNA technology in Humans

· Disadvantages of DNA technology

· Summary

 

 

Learning Objectives

  • To learn about the DNA technology
  • To know about the various types of DNA technologies
  • Application of DNA technology in medicine.

Introduction

In view of the emerging complex diseases that are hindering the quality of life of human populations, Anthropologists in particular Biological Anthropologists in the recent past focused to synchronize the concepts of Biological Anthropology in the study of human diseases that vary from population to population in order to promote the health of the human populations. DNA technology have revolutionized the applications of molecular genetics in understanding the population specific gene expression, susceptibility to a particular disease, evolution of abnormal genes. Understanding the gene expression and its variation from population to population allowed devising gene specific drug therapies. Human being can’t escape from the disease, as it is part and parcel of life. Even though a tiny portion of populations are inherited with certain mutant alleles, but a majority of the humans develop mutant alleles due to exposure to the environment. Exposure to the environment over a period of time enables man to develop certain gene abnormalities that are identified as degenerative diseases. In view of the rapid growth in industrialization and urbanization, innumerable changes are taking place which are witnessed in the form disease prevalence in mid or early 40s. Addressing this issue became great challenge for the scientists including biological anthropologists. Even though the quality of human life is dependent on the genetic endowment, but the interference of environmental factors like social, cultural and biological factors on gene expression override towards abnormalities. Demarcation of health hazards due to gene environmental interaction needs to be tackled on priority basis. In view of the diversity in cultures and life styles across populations, it is imperative to understand the DNA and its changes in specific culture in order to promote and implementing the effective interventional strategies towards the welfare of the humans.

 

What is DNA Technology?

DNA technology is a revolution in biology and is having ever increasing impact on clinical medicine. Earlier genetic diseases could be tracked through pedigree analysis and affected proteins. However no confirmative pathway could be achieved through this technique. Thus a new technology which can directly study the DNA is warranted. Deoxyribonucleic acid (DNA) otherwise the organisms genetic material is inherited from one generation to another generation holds many clues that have unlocked some of the mysteries behind the evolution, disease precipitation, aging and exposure to the environment. Manipulation of genetic material is called as DNA technology. DNA technique makes it possible to take any gene from any species and place this gene in any other organism. DNA technology has plethora applications in our day to day life. DNA technology will be very much useful in identifying certain genetic diseases such as sickle cell anemia and huntington’s disease. Thus there is an ample possibility that certain genetic diseases can be tracked and treated before its precipitation. DNA technology facilitated to develop vaccines which trigger the defense mechanism in the body to fight against the pathogens. Further the development of therapeutic hormones like insulin and human growth hormones are the resultant of DNA technology.

 

          Technological advancements lead to a better understanding of DNA leading to the development of new DNA based technologies like cloning, PCR, recombinant DNA technology, DNA fingerprinting, gene therapy, DNA microarray technology and DNA profiling. DNA technology has brought revolutions in pharmaceutical industry, agriculture, forensic sciences and disease therapies.

 

Cloning

A major component of DNA technology is cloning, which is the process of making multiple, identical copies of a gene by incorporating in an organism like bacteria to use in different applications. This identical or multiple copies of DNA can be characterized or used for various purposes. Cloning gives us pest-resistant plants, vaccines, heart attack treatments and even entirely new organisms.

 

Polymerase chain reaction (PCR)

Polymerase chain reaction represents one of the most significant discoveries or inventions in DNA technology and it lead to a 1993 Nobel Prize award for American born Kary Mullis. PCR is the amplification of a specific sequence of DNA so that it can be analyzed by scientists. Amplification is important, particularly when it is necessary to analyze a small sequence of DNA in quantities that are large enough to perform other molecular analyses such as DNA sequencing.

 

Recombinant DNA technology (Genetic engineering)

Not long after PCR technology was developed, Genetic engineering of DNA through recombinant DNA technology came into limelight in parallel with PCR technology. Altering the DNA by using bacterial derived enzymes like restriction endonucleases that act like scissors in cutting the specific site of DNA is called recombinant DNA technology. This DNA sequence can be inserted into another matched DNA sequence. Restriction endonucleases play an important role to identify the variability between two individuals or groups etc. Restriction enzymes that recognize specific DNA sequences can produce fragments of DNA by cutting different parts of a long strand of DNA. If there are differences in the sequence due to inherited variation, restriction enzymes no longer recognize the site, variable patterns can be produced.

 

 

Gene Therapy

Recombinant DNA technology also helpful in merging the genes into molecular devices that can transport these genes to various cellular destinations. This technique also called as gene therapy. In this technique corrected genes can be delivered into individuals with defective genes that cause specific disease. Different bacteria can be modified through this technique aimed at breaking the harmful contaminants like DDT by producing specific proteins. Currently efforts are in progress to produce genetically designed plants and crops that can produce substances to kill insects. Plant foods can be engineered to have genes that produce specific proteins which slow the ripening process by increasing their shelf life. Many heart and autoimmune diseases have been treated by using this gene therapy. This technique hopefully tackle the issue of huntington’s disease or cystic fibrosis by replacing the defective genes with healthy ones.

 

DNA microarray technology

This technology also known as DNA chip, a latest development in nanotechnology is to study the genome in high throughput manner. This technology facilitates gene expression profiling to understand the specific gene up and down regulation. The up and down regulation of gene allows us to estimate the cancer risk. Because, it has the ability to know the gene expression that is above the baseline level. However it cannot detect the delicate changes in gene expression that causes specific disease.

 

DNA profiling

Methods that are used to describe DNA profile include restriction fragment length polymorphism (RFLP) and short tandem repeat profiling (STR). In RFLP DNA will be cut into different lengths by restriction enzymes and then the segments are separated based on size through electrophoresis. STR will facilitate many copies of a small section of DNA by using specific enzymes. Genes from one organism can be inserted into another organism to produce nutritional and pharmaceutical products. For ex. Cow genes have been modified so that it can produce vitamins or insulin in its milk in bulk. Similarly plants genes also modified to produce desired quantity, taste with added nutritional values. This will play a major role in future in increasing the supply of both food and energy needed by the world’s growing human population.

 

Application of DNA technology

DNA technology has revolutionized biology and is having an ever increasing impact in pharmacology, genetic engineering in disease prevention, in increasing agricultural growth, in detection of disease and crime (forensics) etc. Some fields that have shown remarkable growth due to advances in DNA technology include: forensics, bioinformatics, pharmacology, nanotechnology, archaeology and anthropometry. DNA extracted from archaeological specimens can be used to address anthropological questions. This helps in tracking DNA evolution, migratory patterns and species evolution over the ages. Though the DNA technology is relatively new area of research but it has enormous debate. It will likely continue to be public debate and have its impact on medical diagnostics, therapeutics, forensics and genetic profiling.

 

In the recent past there has been rapid progress in the human genome project and biotechnologies. These advances result in many complex datasets associated with in depth knowledge, e.g., genome sequences of many species, microarray expression profiles of different cell lines, single nucleotide polymorphisms (SNPs) or mutations in the human genome, etc. Human genome has about 30,000 genes, which, surprisingly, only account for ~3% of the genome. The expression of these genes, i.e., the amount of protein products to be made in a cell, is tightly regulated so as to meet the requirements of specific cells and for cells to respond to changes in their environment.

 

DNA technology in medicine

  The emergence of the DNA technology has been driven great strides in understanding fundamental life processes and the ability to investigate problems that had previously been unapproachable. The advances made possible by DNA technology have profound implications for the future of medicine for they have placed us at the threshold of new methods of diagnosis, prevention, and treatment of numerous human diseases. Hormones, vaccines, therapeutic agents, and diagnostic tools developed using different DNA technologies are already greatly enhancing medical practice.

     DNA technology has attained a commonplace in day to day life, as new products from genetically altered plants, animals and microbes became available for human use. Dolly (Sheep) in 1997 stood in headlines as the first successful cloned large mammal. Thereafter many advances have taken place in medicine towards treatment (ex. Cancers). Now because of cloning, many organs and tissues can cloned. Scientists visioned that, DNA technological applications are one of the new frontiers in science with tremendous growth and discovery potential. DNA technology made it possible to treat different diseases by inserting new genes in place of damaged genes in the body. Thus it has brought many changes in the field of medicine and introduced such methods of treating diseases and drug delivery.

 

   The first two commercially prepared products from recombinant DNA technology are insulin and human growth hormone, both of which are cultured in the Eschericia Coli. Patients with diabetes fail to produce requisite amount of insulin, facilitating the processing of sugars from food into energy that the body can use. In the past patients use to take insulin obtained from pigs and cows, however, non human insulin often causes allergic reactions in many diabetics. With the advent of recombinant technology, now we could able to produce safe human insulin. In this technique, human insulin gene is isolated and inserted into plasmids, which are transformed to either bacterial or yeast cells, wherein insulin is synthesized on the human code. The purified insulin is identical to human insulin are absolutely safe.

 

       Human growth hormone is a polypeptide hormone. It functions for proper growth, reproduction of the cells and regeneration. It is secreted by somototroph cells preset in the pituitary gland. In recent years, DNA technology has helped to develop many growth hormones. Dwarfism can be effectively tacked with this technique.

 

   Monoclonal antibodies are used to produce vaccines against different viral infections. When body is encountered by foreign object, immune system of the body releases specific protein called as antibody. Hybridoma technique made it possible to produce monoclonal antibodies where lymphocytes or B cells joined with myeloma cells to produce hybridoma. The antibodies released by hybridoma is called monoclonal antibodies, which are used to produce vaccines against several viral infections. Antibiotics are the substances used to fight against bacterial infections and other microbes causes infections in the body. Alexander Fleming discovered penicillin for the first time in 1928 using the recombinant DNA technology.

 

    Similar to insulin technology, edible vaccines to prevent widespread diseases in developing countries could be achieved efficiently through DNA technology. Edible vaccines are cost-effective, easy to manage and store, safe and socio-culturally readily acceptable vaccine delivery system. In this technique desired genes are inserted into plants and then inducing these altered plants to manufacture the encoded proteins whether it is vaccine or other plant substance. Initially it is thought to be useful for preventing infectious diseases only, however its applications has reopened in prevention of autoimmune diseases, birth control, cancer therapy, etc.

 

   Successful expression of foreign genes in plant cells and/or its edible portions has given ways in developing plants expressing more than one antigenic protein. Multi-component vaccines can be obtained by crossing two plant lines harboring different antigens. Adjuvants may also be co-expressed along with the antigen in the same plant. B subunit of Vibrio Cholera toxin (VC-B) tends to associate with copies of itself, forming a doughnut-shaped five-member ring with a hole in the middle (Landridge, 2000). This feature can bring several different antigens to micro fold cells at one time – for example, a trivalent edible vaccine against cholera, ETEC (Enterotoxigenic E. coli ) and rotavirus could successfully elicit significant immune response to all three (Yu and Landridge, 2001). Global alliance for vaccines and immunization deal very high priority to such combination of vaccines for developing countries.

 

    Later several such products to alleviate different conditions were come into existence. For ex. tumor necrosis factor in the treatment of certain cancers; interleukin-2 in cancer treatment, immune deficiency and HIV infections treatment; prourokinase in the treatment of heart attacks; taxol in the treatment of ovarian cancer; and interferon in the treatment of viral infections and certain cancers.

 

      Further, DNA technology allowed development of many tests which are being used to diagnose diseases like tuberculosis and cancers. Similarly other diseases like measles, small pox and hepatitis can be diagnosed by using this application. In the diagnosis process certain pathogens are isolated and identified, and then diagnostic kits are produced when the genome of the specific pathogen is known to eradicate or block its pathogenic activity.

 

Advantages of DNA technology in Humans

DNA technology has the ability to trace the disease history besides management. Every individual in one day or other are subjected to a condition or diseases. This may be the result of inheritance of certain genes from parents or alteration of phenotypes due to environmental mutagens. These mutations cause several diseases like cystic fibrosis, alzheimer’s, heart diseases and chronic infections. These abnormalities can be reverted by exercising the DNA technology by replacing the bad genes with functional copy of the gene in the correct position. This technology will be helpful to slow down the aging process. By understanding the genetics with the help of genetic engineering, we can develop better pharmaceutical products for human sustenance.

 

Disadvantages of DNA technology

DNA technology has certain disadvantages also. Basically genetic engineering uses viral vectors to carry functional genes into the body, and the consequences of the viral genes on human body is yet to be elucidated. The location of the functional genes in genome is also not known. Otherwise these functional genes may replace other important genes rather than the mutated genes, which may lead to new complications. The replacement of defective gene with functional gene may lose genetic diversity. Hence this technology has to be carefully applied keeping the advantages and disadvantages.

 

Summary

  • DNA technology have revolutionized the applications of molecular genetics in understanding the population specific gene expression, susceptibility to a particular disease, evolution of abnormal genes.
  • Even though the quality of human life is dependent on the genetic endowment, but the interference of environmental factors like social, cultural and zoographical and biological factors on gene expression override towards abnormalities.
  • In view of the diversity in cultures and life styles across populations, it is imperative to understand the DNA and its changes in specific culture in order to promote and implementing the effective interventional strategies towards the welfare of the human.
  • Deoxyribonucleic acid (DNA) otherwise the organisms genetic material is inherited from one generation to another generation holds many clues that have unlocked some of the mysteries behind the evolution, disease precipitation, aging and exposure to the environment.
  • Manipulation of genetic material is called as DNA technology.·
  • DNA technology has plethora applications in our day to day life.
  • Different DNA based technologies are cloning, PCR, recombinant DNA technology, DNA fingerprinting, Gene therapy, DNA microarray technology and DNA profiling
  • DNA technology facilitated to develop vaccines which trigger the defense mechanism in the body to fight against the pathogens. Further the development of therapeutic hormones like insulin and human growth hormones are the resultant of DNA technology.
  • The emergence of the DNA technology has been driven great strides in understanding fundamental life processes and the ability to investigate problems that had previously been unapproachable.
  • The advances made possible by DNA technology have profound implications for the future of medicine for they have placed us at the threshold of new methods of diagnosis, prevention, and treatment of numerous human diseases.

 

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References

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  • Landridge W. Edible vaccines. Scientific Am, 283: 66-71, 2000.
  • Shiyanand P, Noopur S. Recombinant DNA technology: Applications in the field of Biotechnology and Crime Sciences. Int J Pharma Sci Rev Research, 1:43-49, 2010.
  • Yu J, Landridge W. A plant based multicomponent vaccine protects mice from enteric disease.Nat Biotechnology, 19: 548-552, 2001.
  • Nussbaum Robert l, Roderick R, McInnes and Huntington F Willard. Genetics in Medicine, Philadelphia: Saunders, 2001.
  • Rimoin David L. Emery and Rimons Principles and Practice of Medical Genetics. London: New York:  Churchill Livingstone, 2002.
  • Old RW, Primrose SB: Principles of Gene Manipulation-An Introduction to Genetic Engineering. Berkeley, University of California Press, 1981
  • Brown TA. Gene cloning and DNA analysis. 4th edition, 1997; 329 -338 18. S.S.Kori
  • Pharmaceuticalbiotechnology. 3rd edition, 2006; 4 – 8
  • Watson JD, Gilman M, Witkowski J, Solder M. Recombinant DNA, Scientific American Books, NewYork, 1992; 345.