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Published byBarnaby Dawson Modified over 9 years ago
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Mutations
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Mutation Permanent changes or errors in a DNA sequence Copied during DNA replication Therefore heritable OR may occur during transcription to mRNA sequence
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Germ Cell Mutation Occur in reproductive cells of an organism Will be passed on to offspring
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Somatic Cell Mutation Occurs in body cells Side effects may be: Negative Positive There may be none
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Normal hemoglobin Sickle-cell hemoglobin Glu Val Normal hemoglobin DNA Mutant hemoglobin DNA mRNA Sickle Cell Anemia
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Causes Exposure to mutagenic agents UV (ultraviolet) radiation Cosmic rays Chemicals – e.g. pesticides X rays
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Types of Mutations Point Mutation a.k.a – Gene Mutation Only one or a few nucleotides are affected Chromosomal Affects multiple genes May affect genes on separate chromosomes
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mRNA Protein MetLysPheGlyAla Base substitution MetLysPheSerAla Replacement of one base by another AAG CCC GGC AAA AAG ACC GGC AAA Substitution
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Possible Results Missense mutation Only one amino acid is changed DNARNA Amino Acid CCC= GGG= Gly ACC= UGG= Trp
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Possible Results Nonsense Mutation Amino acid in middle of protein is changed to a stop codon Protein not complete & inactive DNAAmino Acid GTA AGT CGG=His – Ser - Ala GTA ACT CGG= His – STOP - Ala
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Possible Results Silent Mutation Amino acid is not changed DNARNA Amino Acid CTA= GAU= Asp CTG= GAC= Asp
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Deletion Elimination of one or more base pairs AAG CCC GGC AAA AA CCC GGC AAA ← shift over AAC CCG GCA AA
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Addition/Insertion Placement of one or more base pairs AAG CCC GGC AAA AAG ACC CGG CAA A
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Reading Frame The sun was hot but the old man did not get his hat. Letters = base pairs (3 letters = codon) Words = amino acid Sentence = protein T hes unw ash otb utt heo ldm and idn otg eth ish at.
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Possible Results Frameshift mutation Moves ‘reading frame’ Codon = 3 bases Changes many amino acids Note: May also result in a nonsense mutation
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MetLysLeuAlaHis Nucleotide deletion mRNA Protein MetLysPheGlyAla Deletion Mutation Result: Frameshift
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mRNA = mRNA = GCU ACU CAA UUC 1. 1.Translate the mRNA above. 2. 2.Translate each mutated mRNA below. a) a)GCU ACU CGA UUC b) b)GCU ACG CAA UUC c) c)GCU ACU UCA AUU C 3. 3.What was the result of each mutation? 4. 4.Which would be most harmful?
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Task Page 263 Answer #2 to 7 Omit #6(e) For #5: list a maximum of 10
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#2 – Additions more harmful than substitutions? Substitution May be silent May change only one amino acid Result: minor protein change Addition Changes reading frame Result: completely new protein Exception If substitution resulted in a nonsense mutation
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#3 – Nonsense vs. Missense Nonsense: Translation ends before protein is complete Protein = inactive Missense: One amino acid changed Protein = may/may not function properly Which is more harmful?
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#4 – Causes UV radiation Cosmic rays X rays Chemicals – e.g. pesticides
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#5 – Create Stop Codon Stop codons: UGA, UAA, UAG Change one base to become stop codon: UAU, UAC, UGU, UGC, UGG, UUA, UCA, UUG, UCG, CGA, AGA, GGA, CAA, CAG, AAA, AAG, GAA, GAG
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#6(a) – Harmful? Original strand: AUG–UUU–UUG–CCU–UAU–CAU–CGU met–phe–leu–pro–tyr–his–arg Change to: UAC New protein: met–phe–leu–pro–tyr–his–arg Silent = not harmful Protein unchanged
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#6(b) – Harmful? Original strand: AUG–UUU–UUG–CCU–UAU–CAU–CGU met–phe–leu–pro–tyr–his–arg Change to: UAA New protein: met–phe–leu–pro–STOP Nonsense = harmful Nonfunctioning protein
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#6(c) – Harmful? Original strand: AUG–UUU–UUG–CCU–UAU–CAU–CGU met–phe–leu–pro–tyr–his–arg New protein: met–phe–leu–ala–leu–leu–leu Frameshift mutation = harmful Different amino acids (new protein) insert a C and shift over
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#6(d) – Harmful? Original strand: AUG–UUU–UUG–CCU–UAU–CAU–CGU met–phe–leu–pro–tyr–his–arg New protein: met–phe–leu–pro–ile–ile Frameshift mutation = harmful Different amino acids (new protein) and shift over Delete and shift over
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#7(a) – Single Substitution Arginine → Leucine With the following substitutions: CGU → CUU CGC → CUC CGA → CUA CGG → CUG
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#7(b) – Single Substitution Cysteine → Glutamic acid Cannot be done with one base pair substitution
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#7(c) – Single Substitution Serine → Threonine With the following substitutions: AGU → ACU AGC → ACC UCU → ACU UCC → ACC UCA → ACA UCG → ACG
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#7(d) – Single Substitution Isoleucine → Serine With the following substitutions: AUU → AGU AUC → AGC
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