الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
SUMMARY
DNn is onE of the nucleic acids present in all cells.
[t is prc”:;en tin the nue 1CU’3 in the ehr omosomes. l n humans
therE are ~3 pairs of homologous chromosomes, one half of
~Jhich ”,H”e dcr-i ·.red from the mother ”egg” and the other hal f
.from the rathe’” ”,::.perm”. It’s molecule is a polymer (a large
molecule c on t e i rr i rrq r”epeatillg units) made up of nuc Le ot i de s .
Hll?l-e are about 3,; 1Q9 nucl e ot i de-s in the DNA of each set of
chrom050nJE’S in c:l human cell Gnd thus there is an enormous
number of diFferent sequence of bases possible.
Dr\IA mol ecul e is composed of a five carbon sugar (,..•,. .
dGo~yribose). phosphoric acid, and four nitrogen basE’S, Two
of which are pur~nes which are adenine <AI and Guanine (G) ,
tho:? other ”we pvr Lm i d i ne bases ~”Jhir:h are thymine (T) and
c·~tosinE’ (C) • Each basE is chemically linked to a
d~o.cyribosr.? in a B-D configuration forming a compound called
nucleoside. A phosphate group also is attached to the sugar
of each nucleoside yielding a nucleotide. It cosists of two
POlYPEptide chains twisted around one another forming a
double stranded heli~. Each base is paired to a base in the
o t.her ~,tt .:Jnt! by h vdr ogen bonds, ~’Jhich are the main force
It () 1 rl i 11q t hr’”, t r ,’11 rl e; ~.0 q l!’ t h ~”’. Th F.” AT p air h,J. S
honds and CO pair has three hydrogen bonds.
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n great deal of informations about gene structure and
expression can be abtained by direct determination of the
sPQuence of basES in DNA molecule. Sever al techniques are
available for base sequencing but no technique can determine
the sequenCE of basEs in an entire chromosome in a single
e::periment, so chromosomes are first cut into
few hundered base pairs long, a size that can
~asily to obtain the sequence of a long stretch
set of over lapping fragments is prepared the
fragments, a
be sequenced
of DNA. a
sequence of
each is det~rmined and all sequences are then combined.
1- Molecular Hybridi~ation and DNA probes.
~- Oligonucleotide probes.
3- DtH\ Fre ct Ionati on.
1- Cloning of recombinant DNA.
DNA is considered the genetic material in the nucleus
of cells1 as it satisfies the follOWing essential
requirments for the genetic malerial:
a.1 Cori s t arrcv of amount in evenly.
bJ [art~’( all the in~o~mation needed to direct the
specific organisat.
c) Replic;tte: e c c ur a l v ,
dJ It is capable of undergoing occasional mutations.
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It is also important in direction of protein synthesis
where one strand of DNA SErves as a templete for the
synthesis of an RNA strand, Each set of three DNA base pairs
or triplet codes for an amino acid. all amino acids are
coded by mor-e than one codon.
where as most normal undividing cell nuclei contain
approHimately equal quantities of DNA, malignant and
premali9nant cells frequently contain much larger and more
variable amounts. So measurement of nuclear DNA content is
therefore potentially suitate for the detection of abnormal
cells in automated screening systems e.g. in human solid
tumours. Also some disorders can be detected prenataly e.g.
Duchenne muscular dystrophy. cystic fibrosis and X-linked
arthinine tr-ans carbamylase deficiency.
The SEquenCe of bas~s in coding rEgions in the DNA
molecule show little or no variation between indiViduals, 50
not havE’ the c ap ac i t v for individualization, mon,
importantly the non coding DNA regions which is a rich
source of variation is causes no two people except identical
h<Jin5 to have the same DNA base sequence. It is the
fundamental level of discrimination which makes DNA typing
5uch ~ pO~’Jer-full tool for” fo,”~n~lc !’5c1l!’nt.l’5t!!l, not Ju!St to
ci:clude but: a lso to i nc lude . Blood. semen, urine, hair as
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well as small tissue samples contain sufficient DNA to
produce DNA fing~rprints. Good DNA stability was found in
br~in ~orteM. lymph nodes and p$oas muscle over a period of
3 weeks post mortem, spleen and kidney showed good DNA
st~bility up to 5 days.
In Forenscic practice DNA typing can be useful in many
conditions e.g rape where semen stains or vaginal swabs
which could be obtained up
where DNA of the sperm head
r~adily compared with the
t-48 hours after intercourse.
can be extracted, typed and
typing of suspect. Also in
D~sputed paternity where familial relationship is
reconstructible by comparing fingerprints of the parents or
close relatives with that of a proband where the questions
of identity in forensic cases often answered. Also DNA
fingerprinting can be useful as many criminal cases where
the typing of body fliuds, hairs tissues, and blood stains
compared with that of the suspect.