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biol lec 7 - Human Genetics Your DNA is 99.9 identical to...

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Human Genetics Chapter 13, 16 Your DNA is 99.9% identical to the DNA of the person sitting next to you So then why are we all so different? · The human genome contains 20,000 to 25,000 genes in about 3 billion base pairs of DNA · .0% variation means variation in the DNA sequence of about 3 million base pairs · cause by mutation Mutations can be classified based on how the DNA sequence is affected 1) Base substitution- changes one base into another DNA template 3’- GGTACGAGAGG- 5’ mRNA: 5’-CCAUGCUCUCC-3’ 2) Insertion- 1 or more extra bases are added The T is red in the first and the A is red in the second Protein: Met-Leu-Serà Met-His-Leu 3) 1 or more bases are removed Protein: Met-Pro Mutation can be classified based on what happens to the protein product 1) Missense Mutation · Base substitution that changes 1 amino acid into another · Can be neutralà change does not alter phenotype Example: change a negatively charged amino acid with another negatively charged amino acid 2) Nonsense Mutation · changes a sense codon into a nonsense codon Sense=specifies an amino acid Nonsense=specifies a stop codon · -results in nonfunctional protein that is shorter than normal 3) Silent Mutation · Point mutation that does not change amino acid sequence · Happens because genetic code is degenerate Some amino acids are specified by multiple codons Example: GGU, GGC, GGA, GGG all code for Gly 4) Frameshift mutation · Addition/deletion of multiples of 1 or 2 base pairs · Amino acid coding sequence downstream of mutation is incorrect · Results in nonfunctional protein Summary: Different Types of Mutation a) Classified by effect of DNA · Base substitution · Insertion · Deletion b) Classified by effect on protein · Missense · Nonsense · Silent · Frameshift *a single mutation could fall into more than 1 category
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How do mutations happen?
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