武汉大学生命科学学院：《分子生物学》英文版 CHAPTER 15 The Genetic Code

Welcome each of You to My molecular Biology class @博来字 Wuhan University

Welcome Each of You to My Molecular Biology Class

Molecular Biology of the Gene 5/E --Watson et al. (2004) Part I: Chemistry and Genetics Part: Maintenance of the genome Part ll: Expression of the Genome Part IV: Regulation Part v: methods 3/22/05 Wuhan University

Molecular Biology of the Gene, 5/E --- Watson et al. (2004) Part I: Chemistry and Genetics Part II: Maintenance of the Genome Part III: Expression of the Genome Part IV: Regulation Part V: Methods 3/22/05

Part III: Expression of the Genome Ch 12: Mechanisms of Transcription Ch 13: RNA Splicing Ch 14: Translation Ch 15: The Genetic Code

Part III: Expression of the Genome Ch 12: Mechanisms of Transcription Ch 13: RNA Splicing Ch 14: Translation Ch 15: The Genetic Code

● Molecular Biology cours CHAPTER 15 The genetic code 博字 Wuhan University

CHAPTER 15 The Genetic Code •Molecular Biology Course

The Central Dogma Transcription CpNA=RNA=→ Protein Translation Replication 1 Genetic information transfer from polynucleotide chain into polypeptide chain 2. Take place in ribosomes. 3. tRNAs recognize codons

DNA RNA Protein Replication Transcription Translation The Central Dogma 1. Genetic information transfer from polynucleotide chain into polypeptide chain. 2. Take place in ribosomes. 3. tRNAs recognize codons

CHATER 15 The Genetic Code Topc1: THE CODE工s DEGENERATE 4/22/05 @博共字 Wuhan Universit

Topic 1: THE CODE IS DEGENERATE CHAPTER 15 The Genetic Code 4/22/05

second position Many amino UUU UCU he UUC ucc ser uac y ucc cysg acids are UAA'I stop UGA stop A eu specific ed by UUG UCG UAG stop UGG TrpG more than CUU CCU CUC CCC CAU His cG U CUA CCA Arg& aone codon CUG CCG 0cc翼 degeneracy AUU ACU AAU AGU Asn AUC lle m(简并性) ACC AAC AGC Thr AUA ACA AAA AGA Codons AUGt Met ACG AAG AGG ArgG GCU GAU GGU u specifying GCC Asp GGC Val the same GUA GCA GAA GAA GUG GCG GAG Glu G amino acid Chain-terminating or"nonsense" codons t Also used in bacteria to specify the initiator formyl-Met-tRNA Met are called TABLE 15-1 synonyms The genetic code 同义密码子

Many amino acids are specified by more than one codon￾degeneracy (简并性). Codons specifying the same amino acid are called synonyms (同义密码子). TABLE 15-1 The Genetic Code

Detail 1: Code Degeneracy 1 Often, when the first two nucleotides are identical the third nucleotide can be either C or U without changing the code. A and G at the third position are interchangeable as well 2. Transition in the third position of a codon specifies a same amino acid. Transversion in this position changes the amino acid about half the time

Detail 1: Code Degeneracy 1. Often, when the first two nucleotides are identical, the third nucleotide can be either C or U without changing the code. A and G at the third position are interchangeable as well. 2. Transition in the third position of a codon specifies a same amino acid. Transversion in this position changes the amino acid about half the time

O--C-C-C-CHa NH H CH3 NH H e accepon sucIna Istom TwC CCCCCUYA GGGGGCloop UGCCCU°A GUT ACGGG.C anticodon anticodon anticodon (CIAG mRNA3匚回UCs AG codon mRNA3匚cuc5 CUG CUC Figure 15-1 Codon-anticodon pairing of two tRNA Leu moleculars

Figure 15-1 Codon-anticodon pairing of two tRNA Leu moleculars CUG CUC

Code degeneracy explains how there can be great variation in the AT/Gc ratios in the dna of various organisms without large changes in the proportion of amino acids in their proteins

Code degeneracy explains how there can be great variation in the AT/GC ratios in the DNA of various organisms without large changes in the proportion of amino acids in their proteins