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DNA Sequencing Laure n Schro er

DNA Sequencing

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Page 1: DNA Sequencing

DNA SequencingLauren Schroer

Page 2: DNA Sequencing

What is DNA Sequencing?

• DNA Sequencing is a technique used to determine the order of nucleotides in a gene.

Page 3: DNA Sequencing

Steps in DNA Sequencing

• DNA Sequencing consists of four main steps:– Polymerase Chain Reaction (PCR)– Sequencing Reaction– Gel Electrophoresis – Computer Scanning

Page 4: DNA Sequencing

Step 1: PCR

• Chromosomes (50-250 million bases long) are multiplied and broken up into shorter fragments.

Page 5: DNA Sequencing

Step 2: Sequencing Reaction

• Reaction is done with dideoxyribonucleotides (just like regular DNA without 3’ hydroxyl group), which when added to the end make it impossible for the DNA to elongate.

• Restriction enzymes cut at these dideoxyribonucleotides. (Ex: Dideoxy-T)

• The place on the strand that is cut is random each time so eventually the cut strands will end with every individual T (or A,G, or C), in the sequence.

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Step 3: Gel Electrophoresis

• The fragments are set in and then separated by Gel Electrophoresis.

• Flourescent dyes are used to identify the end nucleotide (if it is an A, T, G, or C).

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Step 4: Computer Scanning

• Computers ‘read’ the sequence from the gel and interpret the colors and print a sequence of nucleotides across the top.

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Limitations

• Currently only 500-900 bases can be sequenced with each read.

• Less expensive methods are less accurate.

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Ethical Concerns

• Some people believe that a person’s DNA sequence is their business, and their business only, and if DNA sequencing becomes too common it could be abused.

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Sources• "How Do We Sequence DNA?" How Do We Sequence DNA? Web. 23

May 2012.<http://seqcore.brcf.med.umich.edu/doc/educ/dnapr/sequencing.html>.

• "Tiny Reader Makes Fast, Cheap DNA Sequencing Feasible." ScienceDaily. ScienceDaily, 26 Mar. 2012. Web. 23 May 2012. <http://www.sciencedaily.com/releases/2012/03/120326160651.htm>.

• "DNA Sequencing, Without the Fuss." ScienceNOW. Web. 23 May 2012. <http://news.sciencemag.org/sciencenow/2012/03/dna-

sequencing-without-the- fuss.html>.

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