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Biological Sciences 210 - Genetics and Molecular Biology. Fall, 2006. Sequence of the CF Gene. The 4 Nucleotides in DNA. DNA Structure. The DNA Double Helix. E.M. of Prokaryotic Genome. Electron Micrograph of Plasmids. Genes and Intergenic Regions. Chromatin Structure.
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Biological Sciences 210 - Genetics and Molecular Biology Fall, 2006
Missense Point Mutation Wild-TypeMissense Mutant • DNA 3'-TACTTTGTCGGTCCA…-5' 3’-TACTTTGTAGGTCCA…-5' • mRNA 5'-AUGAAACAGCCAGGU…-3' 5’-AUGAAACAUCCAGGU…-3' • Protein fMet--Lys-Gln--Pro-Gly… fMet--Lys-His--Pro-Gly…
Nonsense Point Mutation Wild-TypeNonsense Mutant • DNA 3'-TACTTTGTCGGTCCA…-5' 3'-TACATTGTAGGTCCA…-5' • mRNA 5'-AUGAAACAGCCAGGU…-3’ 5'-AUGUAACAUCCAGGU…-3' • Protein fMet--Lys-Gln--Pro-Gly… fMet
Silent Point Mutation Wild-Type Silent Mutant • DNA 3'-TACTTTGTCGGTCCA…-5' 3'-TACTTTGTTGGTCCA…-5' • mRNA 5'-AUGAAACAGCCAGGU…-3’ 5'-AUGAAACAACCAGGU…-3' • Protein fMet--Lys-Gln--Pro-Gly… fMet--Lys-Gln--Pro-Gly…
Frameshift Mutations • READING FRAME - Translation of an mRNA must start at the appropriate AUG of the mRNA and work along the mRNA in a 5' ----> 3' direction, reading the mRNA in units of 3. It must read in the exactly correct sequence of 3-base codons. • Demonstration: • THE FAT CAT ATE THE BIG RAT • HEF ATC ATA TET HEB IGR AT
Frameshift Mutation • Frameshift mutations change the reading frame of the messenger RNA. • For example: Template strand of DNA • 3'-TACAGAGTGCTGCAT…-5' • 5'-AUGUCUCACGACGUA…-3' mRNA • AUG UCU CAC GAC GUA… codons • fMet -- Ser -- His -- Asp -- Val… • Through a deletion, the DNA strand loses the fifth base in the sequence above: • 3'-TACAAGTGCTGCAT…-5' • 5'-AUGUUCACGACGUA…-3' mRNA • AUG UUC ACG ACG UA… • fMet-- Phe -- Thr -- Thr…