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THE EAGLE is a pub in Cambridge city centre. It is a popular
place for students and professors for socialization and lunch. On 28/2/1953
Francis Crick interrupted patrons lunchtime to announce that he and his colleague
James Watson had discovered the Secret of Life after they have come up with
their model for a 3D structure of Deoxyribonucleic acid. DNA stores hereditary
information that is passed on from one generation to next and holds the key to
the complex world of the cell. Watson and Crick model of DNA structure appeared
as a single page article in the journal Nature on 25/4/1953which marked the
beginning of a new branch of science, Molecular Biology. The climax of the
first 50yrs of DNA revolution and molecular biology came in 2003 with the completion
of Human Genome Project It marked the end of Vitalism and life was explained on
the basis of chemistry and physics. If the twentieth century was the age of computer
revolution and information technology, the twenty-first century will be the age of
genetic revolution and it is interesting to review the progress from the double-helical structure of DNA to the present age of gene editing and genomic
medicine. DNA was isolated in 1869 by Swiss scientist Dr Friedrich Miescher
from hu-man white cells which he called Nuclein. Oswald Avery's experiments on
mice confirmed DNA as the hereditary material in 1944. Other scientists like
Phoebus Levine, Erwin Chargaff and Linus Pauling attempted to figure out the structure but
proved wrong. Rosalind Franklin and Maurice Wilkins were biophysicists at Kings College,
London and X-ray crystallography studies by these two scientists proved a
fundamental clue for Watson and Crick in elucidating the structure of this
molecule. The famous photograph of DNA by Franklin, photograph 51, as compared
to different cardboard models by Watson and the last one proved correct. DNA
con-sits of two anti-parallel helical strands composed of RIBOSE and PHOSPHATE groups
as backbones connected by four nucleotides, namely, Adenine, Thymine, Cytosine
and Guanine. Adenine always paired with Thymine and cytosine with guanine which
suggested a possible copying mechanism for the genetic material. The double
helix has made many important turns from its origin in Cavendish laboratory and
the Eagle pub in1953. Deciphering The Genetic Code, Recombinant DNA Technology,
Sequencing The Nucleotides, Gm Crops, Evolutionary Biology, Biotechnology,
Genetic Finger Printing And Completion Of Human Genome Project are some of the
achievements since 1953 with 24 Nobel prizes awarded to research in genetics or
molecular biology. Most importantly it was possible for scientists to confirm; Darwin's
theory of evolution after 144years.
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Post-Genomic Era
During the 50 yrs after Francis Crick's announcement in the
Eagle, the famous molecule has influenced medicine, biological sciences and law
to a great extent. DNA is no longer a matter of interest only to scientists
working in university laboratories, but it affects society as a whole. But
the science of molecular biology has a long way to go. Cancer has to be
conquered, effective and safe gene therapies still to be developed, and genetic
engineering has to realise its full potential of making safe food and medicines.
Translational researches have been modest from laboratory to clinics in the last
17years after the human genome project, but all will come in the next few decades.
Human genome project started in1990 and completed in 2003
was a major scientific endeavour. It has facilitated the following discoveries
or advancements.
◦ Discovery of nearly 10,000 single-gene disorders out of
an estimated 20,000 to 25,000 protein-coding genes located in the chromosomes.
◦ Faster identification of faulty genes in days rather than
years.
◦ More than 2000 genetic tests for diagnosis and risk
assessment.
◦ About 350 biotechnology products currently in clinical
trial.
◦ International Hap Map project completed in 2010 to
describe the common pattern of genetic variation
◦ Study of genomes of other organisms based on the
knowledge from the human genome project.
◦ The drastic decline in the cost of sequencing
◦ Pharmaco genomics evolved as afield to study genetic
variation and response to drugs.
◦ DNA based therapy for cystic fibro-sis, childhood motor neuron
disease, gene therapy for haemophilia, sickle cell disease and cancer, all in
the early experimental stage.
◦ UK 100,000 genome project, a first national project of its
kind in the world, to sequence rare genetic diseases, some infectious diseases
and common cancers of UK patients completed 6/12/2018
◦ Human Microbiome project started in 2007 and concluded
in 2016 studies the genomes of the microbial flora involved in health and
disease.
◦ Earth Microbiome Project started The Future in 2010, is
an ongoing project to survey The future is in the collection of deform centres
all over the world to microbial genetics in much environ-global knowledge
resource, translations of the planet.
◦ Earth Bio-genome project start-ed in 2018, is an ongoing
project to sequence and classify the genomes of Earth's eukaryotic
biodiversity, over a period of 10 years.. It is an ambitious international
project to map the genomes of all known animals and plants except bacteria and Achaea,
roughly 1 .5million species. It will open up new avenues to treat infections,
new drugs antmnrove food production.
◦ International Cancer Genome Consortium started in 2008,
is an ongoing project by the world's leading and genomic researchers including to
study 50 major cancers of global
◦ Synthetic biology, a disciplinary branch of biology andneering
to design and build biological systems capable of producing biofuels, insect
resistant crops, transplantable organs and DNA synthesis.Mycoplasma
Laboratorium is an example of a partially synthetic species of mycoplasma
bacterium produced in 2010 at Craig Venter institute in the USA.
◦ Phage therapy using genetically engineered virus was
successfully used for the first time in the world in a Lor Fdon hospital to
treat severe antibiotic-resistant bacterial infection in a trans-plant
patient in 2019. This is a new chapter in the management of severe bacterial
infection as the scientists, after extensive trials with thousands of combinations
of phages, were able to use the right cocktail of modified viruses to fight the
bacterial infection Phages are a type of virus that infect bacteria and phage
therapy has potential applications in medicine, agricultural studied the
genomes of the micro bialand veterinary science.
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The Future
The future is in the collection of data from centres all
over the world to a global knowledge resource, translation of laboratory
findings to clinical medicine and from reading to writing DNA. Moral, ethical
and legal implications will be enormous. For the immediate future DNA based
medical treatment will be unaffordable for any health service. Following are
areas in molecular biology and genetics where rapid progress is being made in
the top centres in the USA and UK.
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Gene Therapy
Gene therapy is an experimental technique that uses genes
to treat or prevent disease. It can be done by replacing a mutated gene that
causes disease by a healthy copy of a gene, inactivates a mutated gene or by
introducing a new gene to fight disease. There are a variety of diseases, genetic
and non-genetic, which can potentially be treated by gene therapy. Haemophilia,
Cystic fibrosis, Thalassemia, Sickle cell anaemia, cancer and AIDS are some
examples. There were more than 2000 clinical trials since 1989 and most of them in phase one stage, with limited success in certain conditions.
Stem Cell Research
and Regenerative Medicine
Stem cell research and regenerative medicine are
sub-divisions of molecular biology. Genomic editing of stem cell and
reprogramming of mature cells to pluripotent stem cells are exciting possibilities
in biology and medicine. Over the last 30 yrs, bone marrow replacement therapy
has been practised for conditions like leukaemia and lymphoma with some success.
Organ donation and transplants might become a thing of the past if the safety
of the techniques confirmed by further clinical trials. There was a report last
year from Rom about the success of stem cell transplants in seven children with
congenital immune deficiency.
Precision Medicine
Precision medicine is a young and growing field started in the USA in 2015 and a pilot project is in place in 2018 with 10,000 volunteers It
is a concept to pre-vent or treats diseases based on one's genome, environment
and lifestyle. It is also called personalised medicine but is not literally
focused on one individual patient. The population is classified into subpopulations
based on genome, lifestyle, age, gender etc., and diagnostics, therapeutics and
prevention-focused on the particular profile of the group. Pharmacogenomics is
part of precision medicine and it aims at developing safe and effective
medicines based on the genes of the sub-populations.
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Mitochondrial
Diseases
Mitochondrial diseases are a group of rare disorders caused
by dysfunction of mitochondria and transmitted from mother to all children.
Though rare, mitochondrial diseases are extremely complex and they can cause
virtually any symptom in any organ at any age. Mitochondrial replacement
therapy is a type of IVF which involves genetic elements from three people. The
nucleus from fertilized egg of parents is implanted into a donor egg from which
the nucleus has been removed resulting in THREE PAR-ENT BABIES. World's first
three-parent baby was born in Mexico in 2016 and many more are on the way.
Telomeres and
Immortality
The telomere is a region of repetitive nucleotide sequences at
each end of a chromosome which protects the chromosomes from deletions or from
fusion with neighbouring chromosomes. Over time, due to cell division, the telomere end becomes shorter. They are replenished by an enzyme Telomerase
Reverse Transcriptase. In 1977 Dr Elizabeth Blackburn discovered the unusual nature
of telomeres and the role of telomerase in protecting the chromosomes. Studies
on mice suggest that reactivating the enzyme telomerase can reverse ageing.
Discovery of the molecular structure of human telomerase enzyme in 2018 by
California scientists should kickstart the development of drugs to lengthen
telomeres. At present, there are at least 20 biotechnology companies in the USA
already engaged in research in the area of age-related illnesses and ageing
itself. Experiments on dogs to lengthen telomeres is expected to commence soon
and if successful, human beings may be next.
Gene Editing and Gene
Silencing
Gene editing rewrites DNA with the potential to correct harmful prevent
and treat human diseases. There are different ways to edit genes but the greatest
achievement in recent years is by a technique called CRISPR/CAS9 sys.tem. Two
cancer patients were treated recently by this method at the university expected
to be published in peer-reviewed journals. Gene silencing is the regulation of
gene expression by RNA interference with the possibility of therapeutic
application in cancer, infectious diseases and neurological diseases. There is
a recent report from London about successful gene silencing method in Huntington
disease and Porphyria. The difference between gene editing and gene silencing
is, only one treatment is needed for the former while multiple treatments are
needed for the latter and hence more expensive.
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CRISPR /Cas-9 System
CRISPR/CAS-9 system or "Clustered Regularly Interspaced
Short Palindromic Repeats" editing tool invented by Dr Jennifer Doudna and
Dr Emmanuelle Charpentier in 2012 marks a new era in molecular biology. It is
an immunological mechanism detected in bacteria that degrades invasive viral or
other exogenous DNA which enables scientists to rewrite the genetic code with
the power to cure diseases, create new sources of food and energy and even
redesign any species, including humans, for our own ends. This method of gene
editing has created great interest in the scientific world as it is faster,
cheaper and a precise method to alter the genome of plants, animals and humans.
The pros and cons of this technology will be known in a decade or two.
Car T Cell
Immunotherapy for Cancer
Chimeric Antigen Receptor T cell therapy is reprogramming the body's immune system to attack the cancer cell. This involves introducing
genetically modified virus into T white cell to manufacture chimeric antigen
receptor T cells or CART cells which in turn attacks cancer cells. Research is
now underway to use CART cell therapy against blood cancers and solid tumours.
Hereditary and
Congenital Disorders in India
All the known hereditary and genetic conditions are
prevalent in India, most common is haemophilia A, Sickle cell disease, Beta Thalassemia,
Cystic fibro-sis, spinal muscular atrophy and Down's syndrome. There is a
genetic link in almost all diseases and it is particularly true with congenital
heart disease and some neurological conditions which present in childhood. With
nearly 5000ethnic groups practising endogamy and consanguinity, the country is
a living laboratory for genetic and congenital disorders through the exact risk
factors and gene mutations are not known at this stage. Because of the population
size, recessive conditions may be a special problem in some communities. Based
on the Bradford study in an Asian community in the UK, genetic risk doubles in
cousin marriages,6% compared to3% in the general population. Though India was not
involved in the human genome project, the country has given due importance to
genetic research in the present century, Indian genetic dis-ease database and
Indian genetic variation consortium is examples. Genome Asia 100K project is a
recent initiative by Nanyang Technological University, Singapore, to sequence
the genome of100,000 Asians including 50,000 Indians and when complete will
take the country to the era of precision medicine.
Economic Implications
of DNA Based Therapy
Affordability is a big obstacle at pres-ent in genomic
medicine. For example, the cost of gene therapy for spinal muscular atrophy is
$750000/ for the first year and $ 375000/ per year thereafter. For acute
lymphoblastic leukaemia is $475000/ for one treatment. One has to be
optimistic that it might come down with further progress in biotechnology as
in the case of sequencing a human genome. The total cost of the human genome
project was $2.7 billion during the period 1990 to 2003 and at present$ 1000/
for a person and can be done within a day or two. Let the famous double helix, humanity
is the most mysterious molecule, feed the world with safer food, help us to conquer
cancer, problems of old age and all the genetic diseases for which there is no
effective treatment at present!
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