Point Mutations A point mutation is a single nucleotide change Substitute on nucleotide for another Usually caught and corrected cid 127 Only a fraction of the human genome codes for proteins Types of point mutations Silent doesn t change the outcome of protein cid 127 Missense codes for incorrect amino acid Nonsense prematurely stops translation Sickle Cell Anemia Produced by a missense mutation that causes hemoglobin to be hydrophobic Substitutions in the third nucleotide are less likely to affect the protein Frame shift mutations change all codons that come after the mutation cid 127 Only shifts frame if the mutation is after the start codon Chromosome mutations Inversion flipped and reinserted Deletion region lost Duplication region is repeated and changes gene dosage Translocation region from one chromosome attached to another chromosome Polymorphisms and Genetic Diversity Every time a change in the genotype occurs a new allele is formed cid 127 Only changes in gametes can be passed on cid 127 May or may not have phenotypic impact Used as markers to screen for other genetic variations cid 127 Genetic variation is the raw material on which evolution operates RNA Processing in Eukaryotes Introns are transcribed and then removed cid 127 Must be cut out to show introns Exons are transcribed and then expressed After splicing caps and tails are added to the ends Ends protect mRNA from being broken down and direct it to translation machinery tRNA is a translation molecule rRNA exists in the ribosome Before the start codon there is a code for the ribosomal binding site Single nucleotide Polymorphisms SNPs can be used to see genetic similarities and differences between related organisms cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127
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