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How do they read Dna strs and snps

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  • How do they read Dna strs and snps

    This may be a silly Question but DNA is at the atomic level and I don't understand how they can find and read all the bases at that level.

  • #2
    Really molecular rather than atomic level. The basic phenomenon is that complementary bases bind to each other by hydrogen bonding, rather strongly under the right conditions. STR's and SNP's are pulled out of a soup of your fragmented DNA sample by binding under appropriate conditions to short DNA "probes" that are complementary to whatever STR or SNP they are meant to detect. Exactly how the probes are designed and constructed, and how the binding is detected and scored, somebody else will have to explain. But for purposes of STR's and individual SNP's, it is a question of detecting specific fragments, rather than actually sequencing long strands of DNA. For the BigY, I believe actual sequencing is involved, starting from longer fragments that are detected by binding to a particular probe. Another very fascinating story.