突变的两种方式 Thr)( Gin)(Arg)(GI Codon 1 Codon 2 Codon 3 Codon 4 acAC T GG T WIld-type gene Thr A CAC AGCGCGGT Synonymous substitution Base substitutions Thr Gin Ser)(Gly ACA G T GG T Missense substitution Thr)(Ala)(Ala Frameshift mutation AC A G C"AGcG"TG"GT… A Genetics Ch126
Genetics Ch12.6 一、突变的两种方式
突变的两种方式 Original DNA sequence (a)Base substitution GGG AGT GTA GAT CGT GGG AGT GCA GAT CGT One codon changed A base substitution alters a single codon Three basic types of gene mutations are base substitutions. insertions. and deletions A Genetics Ch127
Genetics Ch12.7 一、突变的两种方式 • Three basic types of gene mutations are base substitutions, insertions, and deletions
突变的两种方式 (b) Insertion (c) Deletion GGG AGT GTT AGA TCG GGG AGT GAG ATC GTC An insertion or a deletion alters the reading frame and may change many codons Three basic types of gene mutations are base substitutions. insertions. and deletions A Genetics ch128
Genetics Ch12.8 一、突变的两种方式 • Three basic types of gene mutations are base substitutions, insertions, and deletions
突变产生的机理 1.互变异构化 tautomer:一个质子的位置变化而 改变了碱基氢键的特性。 嘌呤的氨基形式分嘌呤的稀有亚氨基形式 ·(与胸腺嘧啶配对)(与胞嘧啶配对) 造成:A=T→G=C(转换) 互变异构化在DNA复制中自发产生。 A Genetics ch12.9
Genetics Ch12.9 二、突变产生的机理 • 1．互变异构化(tautomer)：一个质子的位置变化而 改变了碱基氢键的特性。 • 嘌呤的氨基形式 嘌呤的稀有亚氨基形式 • （与胸腺嘧啶配对） （与胞嘧啶配对） • 造成：A=T→G=C （转换） • 互变异构化在DNA复制中自发产生
突变产生的机理 Purine and pyrimidine Common forms Rare forms 0- Proton shift bases exist in different forms called tautomers Thymine (互变异构体) (a)a tautomeric shift NH2 Guanine occurs when a proton changes its position Cytosine resulting in a rare tautomeric form Adenine A Genetics ch1210
Genetics Ch12.10 二、突变产生的机理 • Purine and pyrimidine bases exist in different forms called tautomers (互变异构体). • (a) A tautomeric shift occurs when a proton changes its position, resulting in a rare tautomeric form