1.连续性、方向性 Second base c A G A frameshift mutation UUU UCU UAU UGU inserts a new basepair here. Phe 公 Cys Normal DNA UUC ucc UAC UGC Ser ATGACCTTTGATCTAAAG ATGAACCTTTGATCTAAAG UUA UCA UAA Stop UGA Stop Leu 9 TACTGGAAACTAGATTTC DNA UUG UCG UAG Stop UGG Trp CUU cCU CAU CGU strand His Transcription CUC ccc CAC CGC . Leu Pro Arg CUA Reading frames CCA CAA CGA 9 CUG CCG CAG CGG G AUGACCUUUGAUCUAAAG mRNA UGAUCUAAAG First base Third base AUU ACU AAU AGU Asn Ser codor AUC ACC AAC AGC Translation .and new reading frame A ensues in translation. AUA ACA AAA AGA Lys Arg AUG Met/Start ACG AAG AGG Thr Leu Lys Protein GUU GCU GAU GGU Asp GUC GCC GAC cac 0 Frameshifts often lead to G Val Ala Gly premature termination. GUA GCA GAA GGA Glu GUG GCG GAG GGG
1. 连续性、方向性
a91 a3 aas a3 aa11 aa13 aa15 U CIC'IG GIAIA AICIU CICIU UIUIC AIGIC CICIU CIAIU C a82 aaa aas aag aa o aa 12 aa14 aa16 (a)Overlapping code There will be statistical regularities between adjacent amino acid residues Point mutations (red)will be able to change two amino acid residues aa aa2 aaa aa aas aas UCCIGIG A AIAC U CICIU U UICIA G CICICIU CIAIUC (b)Punctuated code Deletions of four nucleotides (or multiples thereof)will restore the reading frame aa aa2 aa3 aa aasaas aa7 aas UCCIG GAIAA CIUC CIUUUICA GIC C CIU C AIUC (c)Unpunctuated code Deletions of three nucleotides (or multiples thereof)will restore the reading frame.This is the actual form of the code
2.密码的简并性 ·密码的简并性：一个 DEGENERACY OF THE Second base GENETIC CODE 氨基酸具有二个以上 UUU uCU UAU UGU Number of Phe Cys UUc UAC UGC 的密码子 codons: ucc Ser UUA UAA Stop UGA Stop Leu UUG UCG UAG Stop UGG Trp G 同义密码子：可以编 CUU ccu CAU CGU HIs cuc Leu cce % CAC cGc 码相同氨基酸的密码 CUA CCA Arg CAA CGA A GIn 子 CUG ccG CAG CGG AUU ACU AAU AGU Asn Ser AUC Ile ACC AAC AGC A Thr AUA ACA AAA AGA s Arg AUG Met/Start ACG AAG AGG G GUU GCU GAU GGU Asp GUC Gcc GAC GGC G Val Ala GUA GCA GAA GGA Glu GUG GCG GAG GGG
2. 密码的简并性 • 密码的简并性：一个 氨基酸具有二个以上 的密码子 • 同义密码子：可以编 码相同氨基酸的密码 子
3 A OH tRNALyS 31 -5 G mRNA (c】
Gly Gly Anticodon Inosine mRNA GGU 5 Codon 3' Inosine(I)can wobble pair with U,C or A
5' 3' 3' 5