SNPsW11 - How much does DNA sequence vary among humans Some...

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How much does DNA sequence vary among humans? Some estimates are that human genome 99.5 - 99.9% similar among individuals Human genome about 3,000,000,000 basepairs So even if there is only 0.1% difference between two individuals, 3 billion x .001 = 3,000,000 nucleotides that differ A locus is a place or position on a chromosome. A locus is monomorphic if all humans have the same DNA sequence at that position A locus is polymorphic if the sequence at the locus varies among individuals The alternative variations at polymorphic loci are called alleles
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Types of polymorphisms:
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S ingle N ucleotide P olymorphisms Change of a single nucleotide at a defined position (locus) in the genome (e.g., A to G) SNPs are the most common genetic variations – new estimates indicate that they occur once every 100 bases Efforts are underway in both the public and private sectors to map all SNPs in the human genome Location of SNPs is important SNPs in non-coding regions of sequence do not change the amino acid composition of proteins Even SNPs in coding regions may not change sequence. However, SNPs that change amino sequence can change function of protein. cSNP = SNP in coding region • synonymous – no change in amino acid sequence • non-synonymous change in amino acid sequence
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The genome of the individuals were compared to the human reference sequence. There are probably about 10 million SNPs occur with a minor allele frequency of at least 5%.
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From the U.S. Department of Energy Genome Programs http://genomics.energy.gov
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hemoglobin beta (HBB)
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SNPsW11 - How much does DNA sequence vary among humans Some...

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