Chapter 8,part C Microbial Genetics
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings B.E Pruitt & Jane J. Stein Chapter 8, part C Microbial Genetics
Mutation Change in the genetic material Mutations may be neutral,beneficial,or harmful Mutagen:Agent that causes mutations Spontaneous mutations:Occur in the absence of a mutagen
• Change in the genetic material • Mutations may be neutral, beneficial, or harmful • Mutagen: Agent that causes mutations • Spontaneous mutations: Occur in the absence of a mutagen Mutation
Mutation Base substitution .Change in one base (point mutation) 。Missense mutation .Result in change in amino acid DNA(coding strand) OACOOCA WNCC AUU DNA(coding strand) OACOUCAAAUC AUD Transcription A.N.acoNdec mRNA oAA8oo的eoAA mRNA Amino acid sequence Me Phe Stop Translation (b)Missense mutation Amino acid sequence Met Lys Phe Gly Stop (a)Normal DNA molecule Figure 8.17a,b
• Base substitution (point mutation) • Missense mutation Mutation Figure 8.17a, b •Change in one base •Result in change in amino acid
Mutation 。Nonsense mutation Results in a nonsense codon DNA(coding strand) TACUUCAAACC AUU TA CAU CA AACC GAU D Transcription 风a.ohcooc.&eoA囚 Aod风风o0 aedech mRNA Met Stop Translation (c)Nonsense mutation Amino acid sequence Phe Gly Stop (a)Normal DNA molecule Figure 8.17a,c
• Nonsense mutation Mutation • Results in a nonsense codon Figure 8.17a, c
Mutation 。Frameshift mutation .Insertion or deletion of one or more nucleotide pairs DNA(coding strand) TACOOCAAACC AUO TACUUCAACCGAUT Transcription ↓ AasAsansse AodA囚oo@&的aAA mRNA Translation (d)Frameshift mutation Amino acid sequence Met Lys Phe Gly Stop (a)Normal DNA molecule Figure 8.17a,d
• Frameshift mutation Mutation Figure 8.17a, d •Insertion or deletion of one or more nucleotide pairs