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روشهایی بررسی و تشخیص جهشها در ژنتییک مولکولی DNA
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We now know how God wrote the book of life
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But do we know how to read the book ?
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Genetic Diagnostics Cytogenetic tests FISH Molecular tests
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Molecular Diagnostics - Diagnosis of infectious diseases - Genetic identification - Diagnosis of genetic diseases
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Genetic Identification - Paternity Testing - Forensics
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Diagnosis of genetic diseases - Somatic rearrangements in cancer - Genetic risk factors - Pharmacogenetics - Mutations in monogenic diseases
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Types of Mutations Tested Disease Point mutations? Deletions & duplications? Few recurrent mutations? Many unique mutations? Also with point mutations? Whole gene? Some exons? Other mutations?
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Most genetic technologies are based on four properties of DNA 1.DNA can be cut at specific sites (motifs) by restriction enzymes 2.Different lengths of DNA can be size-separated by gel electrophoresis 3.A single strand of DNA will stick to its complement (hybridisation) 4.DNA can be copied by a polymerase enzyme DNA sequencing Polymerase chain reaction (PCR)
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DNA can be copied by a polymerase enzyme Polymerase chain reaction (PCR) A method for producing large (and therefore analysable) quantities of a specific region of DNA from tiny quantities PCR works by doubling the quantity of the target sequence through repeated cycles of separation and synthesis of DNA strands 1. PCR: Polymerase Chain Reaction
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DNA can copied by a polymerase enzyme
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PCR can generate 100 billion copies from a single DNA molecule in an afternoon PCR is easy to execute The DNA sample can be pure, or it can be a minute part of an extremely complex mixture of biological materials The DNA may come from – a hospital tissue specimen –a single human hair –a drop of dried blood at the scene of a crime –the tissues of a mummified brain –a 40,000-year-old wooly mammoth frozen in a glacier. In the words of its inventor, Kary Mullis…
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DNA can copied by a polymerase enzyme ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA
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DNA can copied by a polymerase enzyme ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA DNA polymerase C C C C C C G G G G G G G G G T T T T A T T A A A A A A A A
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DNA can copied by a polymerase enzyme
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A C T G DNA template Heat resistant DNA polymerase G, A, C, T bases Forward primer Reverse primer A thermal cycler (PCR machine)
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DNA can copied by a polymerase enzyme
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Modified PCR and non-PCR amplifications techniques ARMS PCR --- point mutations RT-PCR ---- gene expression(qualitative) Gap PCR ---- deletion Real time PCR ---- gene expression (quantitative)
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Modern genetic markers: SNPs ARMS: amplification refractory mutation system Clin Biochem Rev (2006) 27: 63–75 Amplification-Refractory mutation system (ARMS) PCR
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Allele-specific PCR (ARMS test)
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Restriction enzymes cut double-stranded DNA at specific sequences (motifs) E.g. the enzyme Sau3AI cuts at the sequence GATC Most recognition sites are palindromes: e.g. the reverse complement of GATC is GATC Restriction enzymes evolved as defence against foreign DNA DNA can be cut at specific sites (motifs) by an enzyme Sau3AI 2. RFLP: restriction fragment length polymorphism
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ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA DNA can be cut at specific sites (motifs) by an enzyme
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Sau3AI ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA DNA can be cut at specific sites (motifs) by an enzyme
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Sau3AI ACTGTCGATGTCGTCGTCGTAGCTGCT GATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAG CATCGATCGA DNA can be cut at specific sites (motifs) by an enzyme
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ACTGTCGATGTCGTCGTCGTAGCTGCT TGACAGCTACAGCAGCAGCATCGACGACTAG GATCGTAGCTAGCT CATCGATCGA ACTGTCGATGTCGTCGTCGTAGCTGCTGA TGACAGCTACAGCAGCAGCATCGACGACT TCGTAGCTAGCT AGCATCGATCGA DNA can be cut at specific sites (motifs) by an enzyme
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Different lengths of DNA can be separated by gel electrophoresis DNA is negatively charged and will move through a gel matrix towards a positive electrode Shorter lengths move faster
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Different lengths of DNA can be separated by gel electrophoresis DNA is negatively charged and will move through a gel matrix towards a positive electrode Shorter lengths move faster
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Different lengths of DNA can be separated by gel electrophoresis Slow: 41 bp ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA Medium: 27 bp ACTGTCGATGTCGTCGTCGTAGCTGCT TGACAGCTACAGCAGCAGCATCGACGACTAG Fast: 10 bp GATCGTAGCTAGCT CATCGATCGA F M S
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Different lengths of DNA can be separated by gel electrophoresis Recessive disease allele D is cut by Sma3AI: ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA Healthy H allele is not cut: ACTGTCGATGTCGTCGTCGTAGCTGCTGAGCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTCGCATCGATCGA F M S HHHD DD
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Different lengths of DNA can be separated by gel electrophoresis F M S HHHD DD The C282Y mutation, caused by a guanine (G) to Adenine (A) transition, results in the substitution of cysteine by tyrosine in the HFE protein.
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A single strand of DNA will stick to its complement ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA 3.DNA Hybridization
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A single strand of DNA will stick to its complement 60°C ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA
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A single strand of DNA will stick to its complement 95°C ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA 3.DNA Hybridization
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A single strand of DNA will stick to its complement 60°C ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA
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A single strand of DNA will stick to its complement a. Southern Bloting
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A single strand of DNA will stick to its complement Southern blotting (named after Ed Southern)
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A single strand of DNA will stick to its complement Southern blotting (named after Ed Southern)
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A single strand of DNA will stick to its complement
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Array technology: 1.Microarray …… Gene expression 2. CGH array…Genomic imbalances
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DNA can copied by a polymerase enzyme ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT TGACAGCTACAGCAGCAGCATCGACGACTAGCATCGATCGA DNA polymerase C C C C C C G G G G G G G G G T T T T A T T A A A A A A A A 4. DNA Sequencing
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DNA can copied by a polymerase enzyme ACTGT ACTGTCGAT ACTGTCGATGT ACTGTCGATGTCGT ACTGTCGATGTCGTCGT ACTGTCGATGTCGTCGTCGT ACTGTCGATGTCGTCGTCGTAGCT ACTGTCGATGTCGTCGTCGTAGCTGCT ACTGTCGATGTCGTCGTCGTAGCTGCTGAT ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGT ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCT ACTGTCGATGTCGTCGTCGTAGCTGCTGATCGTAGCTAGCT
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DNA can copied by a polymerase enzyme ACTGTCGATGTCGT
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DNA can copied by a polymerase enzyme ACTGTCGATGT ACTGTCGATG ACTGTCGAT ACTGTCGA ACTGTCG ACTGTC ACTGT Fluorescence Time Fluorescence Time TGTAGCTTGTAGCT T C G A T G T etc
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DNA can copied by a polymerase enzyme
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Looking into the future
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