Download DNA is an abbreviation for deoxyribonucleic acid

DNA is an abbreviation for
deoxyribonucleic acid .
-------------------------------------------------------*It is formed in the cells of all living
things ,including the human body .
*The DNA is a very long molecule and
is found in the nucleus of cells
DNA consists of three basic components:
A . A sugar (pentose sugar) ~ dexoyribose which
is oxygen less of the ribose sugar
B. Phosphate group ~ chemically reactive
C. Organic nitrogenous base ~ 4types of
nitrogenous base, 2 purines and 2 pyrimidines
~ purines consists of adenine (A) and Guanine(G)
~ pyrimidines consist of cytomsine(C) and thymine
(T)
In 1962,
James Watson
(from America)
and
Francis Crick (from Britain)
discovered the structure of DNA.
They were awarded a
Nobel Prize.
(A) The sequence of bases in DNA provides
the genetic code to give information to control
the cell activities and is
specific to each species.
(B) The complementary relationship of the bases
in the DNA molecule enables the DNA to
replicate (make an exact copy) so that the
same genetic information
can be passed to the offspring.
The type of protein and enzyme is
characteristic of a species of organism.
Chromosomes are made up
of proteins (e.g.histones)
and nucleic acid (DNA and RNA).
The nucleic acids
carry the genetic code or
genetic formation.
Some interesting information
about DNA
Genetic engineering is an unnatural insertion of a
foreign sequence of genetic codes
in the midst of the orderly
sequence of genetic codes
of the recipient, developed
through millions of years.
Cloning is one aspect of genetic engineering, the part
that allows scientists to use a variety of methods to
duplicate copies of already existing organisms or
genetic material.
But the term "genetic engineering" is
much broader, encompassing a wide
range of procedures designed to alter
genetic material, not only copying
genes, but in some cases, making
completely new proteins.
Introduce the mutations of DNA:
(1) Chromosome mutations
involve changes in the number of
chromosomes per cell or changes in the
gross structure of a chromosome.
These changes are generally observable under
the microscope.
(2) Gene mutations involve the chemical
changes in an individual gene and they
cannot be seen under the microscope.
(1) Induced mutation can be induced artificially to occur
at a higher rate by applying mutagenic agents
(mutagens ). For example:
(a) Chemical mutagens - nitrous acids, base analogues,
 mustard gas, ethyl urethane
 formaldehyde.
(b) Physical mutagens - X rays,
 ultra-violet rays,
 cosmicrays
 atomic radiation.

(E) Changes involve in the addition or loss of
one or more chromosomes.

(a) If change in the addition of one or more chromosomes, mongolism in
man is caused by the
presence of one extra piece of the 21st

chromosome in the cell. Such

individuals have abnormalities

of the face, Eye-lids and tongue

are mentally retarded.

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