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DNA

VIEWS: 6 PAGES: 4

									                                               DNA
Intro
       Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the
        development and functioning of all known living organisms and some viruses.
       In other words (DNA) is the biological make up in every organism.

Aim
        To equipt the Offrs about the basc knowledge about DNA

Sequence
    1. PART 1                       Background

    2. PART 2                      Structure of DNA

    3. PART 3                      Future prospects and Concl




                                                    Part-1
Background of DNA

DNA was first isolated – extracted from cells – by Swiss physician Friedrich Miescher in 1869, when he
was working on bacteria from the pus in surgical bandages. The molecule was found in the nucleus of
the cells and so he called it nuclein.

The DNA molecule was discovered in 1951 by Francis Crick, James Watson, and Maurice Wilkins using X-ray
diffraction. In 1953 Crick described the structure of the DNA molecule as a double helix, somewhat like a sprial
staircase with many individual steps. In 1962 Crick, Watson, and Wilkins received the Nobel prize for their
pioneering work on the structure of the DNA molecule
                                                 Part-2


Structure of DNA

DNA is shaped like a double helix, which is like a ladder twisted into a spiral. Each leg of the ladder is a
line of nucleotides. A nucleotide is a molecule made up of deoxyribose. This is a kind of sugar with 5
carbon atoms), a phosphate group (made of phosphorus and oxygen), and a nitrogenous base. DNA is
made of four types of nucleotide:

       Adenine (A)
       Thymine (T)
       Cytosine (C)
       Guanine (G)




                                                 Part-3
                                   Ways that DNA Changed the World




1 THE SHAPE OF THINGS TO COME


Two intertwining strands of DNA wrapped around a central axis to form a gently curving double helix:
this instantly recognisable structure is one of the 20th century's most powerful icons. Watson and Crick
themselves felt that the double helix was so simple, so beautiful (it's sometimes described as the "Mona
Lisa" of science), that it had to be right, while its enigmatic symmetry made a powerful prediction about
how genetic information is stored and transmitted from one generation to the next.

2 THE GENE EXPLAINED


For centuries philosophers pondered inheritance and how one person can be an amalgam of two
parents. Cracking the structure of DNA explained how the fundamental unit of inheritance - the gene -
works, and how it is replicated from one cell to the next and one generation to another. Now that they
knew the molecular basis of the gene, scientists could understand how it can be damaged, and why such
"mutations" can lead to harmful diseases or, occasionally, beneficial traits that can form the basis of a
new trend in evolution.

3 UNDERSTANDING INHERITED DISEASES
One of the first inherited diseases to be unravelled at the level of DNA was sickle-cell anaemia, a blood
disorder that affects mostly Africans and natives of the Mediterranean region - areas badly affected by
malaria. A single mutation in the gene for the blood protein haemoglobin can affect its ability to
transport oxygen around the body. People who inherit two copies of the same mutation, one from each
parent, have severe symptoms. However, those who inherit just one copy of the mutation do not suffer
too badly; in fact, they are resistant to malaria. The discovery told geneticists much about evolution and
how harmful mutations can increase to relatively high levels within a population provided they confer
some advantage.


4 CURING INHERITED DISEASES


By understanding how a gene can go wrong, scientists can work out ways of putting it right - hopefully.
In April 2002, Rhys Evans became the first child in Britain to be declared cured of an inherited disorder
as a result of gene therapy, which involves "repairing" a defective gene by augmenting it with a healthy
version. Rhys had inherited a defective Gamma C gene from his mother; this meant that his immune
system did not function, making even the most innocuous infection life-threatening. He had spent his
life inside a sterile "bubble". Then a blood transfusion containing his own, genetically modified cells
corrected the defect and enabled the 18-month-old to play outside with his friends for the first time in
his life.

5 PREDICTING INHERITED DISEASE


Some disorders are caused by several genetic defects acting in unison. Cancer is the classic example: it is
caused by a cascade of cellular changes triggered by a series of mutations. But sometimes cancer can
result from a defect in just one gene that runs in a family, such as the breast-cancer genes BRAC1 and
BRAC2. Understanding this has led to the development of breast-cancer tests for women whose families
carry the gene.

6 UPHOLDING JUSTICE


In 1988, Colin Pitchfork was sentenced to life for the killing of a schoolgirl, Dawn Ashworth, after he
became the first murderer to have his DNA matched to that of a tissue sample at the scene of a crime.
What is less well known is that DNA fingerprinting, as it is known, was also used on another suspect who
had already confessed to the same murder. The test proved that the confession was false. DNA
fingerprints have revolutionised criminal investigations and have helped to protect the innocent as well
as to convict the guilty.

7 LOOKING FOR DADDY


Where would Elizabeth Hurley (left) be without DNA testing? DNA tests on a child can establish
paternity beyond reasonable doubt, even in a case where the putative fathers are both brothers
(although this is not the case with identical twins, who share the same DNA sequence).

8 A DOG'S LIFE


DNA tests are used to confirm the pedigrees of pet dogs and cats, racehorses and livestock. They can
establish the identity of illegally collected bird's eggs and the hides of protected species.

9 WHERE WE CAME FROM 1


DNA analysis supports the view that early humans moved out of Africa less than 100,000 years ago to
colonise the world. DNA has shown that the first farmers migrated west from the Middle East across
Europe. It has helped to establish when the first humans moved into Australia, reached the Pacific
islands on boats and crossed the ice-locked Bering Strait into the uninhabited North American continent.

10 WHERE WE CAME FROM 2


DNA tests on ancient bones have shown that Neanderthal man and modern humans are not closely
related. Scientists now believe that Neanderthals, who lived alongside modern humans for thousands of
years, never interbred with their close cousins. DNA tests on living people have revealed other ethnic
and ancestral origins that have been lost over time. The ancestors of many Icelandic women came from
Ireland rather than Norway. Many British Afro-Caribbean men inherited their male Y chromosomes from
white ancestors who were alive at the time of the slave trade.

								
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