Lecture7 markers

Lecture7 markers - Lecture 7 Molecular markers and...

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Lecture 7: Molecular markers and application Types of markers/polymorphism How to assay markers Applications Read: 369-381 Fig. 11.2-13 Table 11.1 10/04/11
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What is DNA Polymorphism? One of two or more alternate forms (alleles) of a chromosomal locus that differ in nucleotide sequence or have variable numbers of repeated nucleotide units. They each present >1% of a species' members. New concepts: 1. Locus: a specific point/region in the genome 2. Alleles: genetic variants of polymorphic loci. 3. No strict WT/mutant classification 4. They do not have to cause phenotypic changes
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Categories of genetic variants Five categories based on size, frequency within individual genomes, and method used for detection 3 Table 11.1
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4 Single nucleotide polymorphism (SNP) Single base-pair substitutions Arise by mutagenic chemicals or rare mistakes in replication Ratio of alleles ranges from 1:100 to 50:50- out of 100 people only 1 has this form and 100 has another form….etc. About 18 million human SNPs identified (23 and me assays 550,000 SNPs) ( Chimpanzee and human have 35 million SNPs and 5 million indels ) Most occur at anonymous loci- (silent mutation) does not give rise to any phenotype Mutation rate of 1 X 10 -9 per locus per generation Useful as DNA markers 11.3
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The origin of human SNPs is determined by comparison to other species Comparison of human and chimpanzee genomes reveals the SNPs that occurred since divergence of these species Human-specific SNP alleles that are shared between individuals indicate recent common ancestry In the example below: The first single base change between humans and chimps is not polymorphic in humans The second single base change is polymorphic between humans 5 Fig. 11.3c
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Pairwise comparison of three personal genomes Single nucleotide polymorphisms in the genomes of three individuals [(Craig Venter, James Watson, and a Chinese man (anonymous, YH)] 6 Fig. 11.2 Differences across the entire genome Amino acid-changing substitutions
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What is a reference genome? reference provides a
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This note was uploaded on 04/03/2012 for the course BSCI 410 taught by Professor Staff during the Spring '08 term at Maryland.

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Lecture7 markers - Lecture 7 Molecular markers and...

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