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02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
02 The Role of DNA in Protein Synthesis
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02 The Role of DNA in Protein Synthesis

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  • 1. The role of DNA in protein synthesis ALBIO9700/2006JK
  • 2. DNA controls protein synthesis• The shape and behaviour of a protein molecule depends on the exact sequence of the amino acids (primary structure)• DNA controls protein structure by determining the exact order in which the amino acids join together when proteins are made in a cell• The triplet code: – The sequence of bases or nucleotides in a DNA molecule is a code for the sequence of amino acids in a polypeptide – The code is a three-letter or triplet code – Each sequence of 3 bases stands for 1 amino acid – Sequence read in 1 direction and on 1 strand of DNA molecule ALBIO9700/2006JK
  • 3. ALBIO9700/2006JK
  • 4. Protein synthesis• DNA molecule unwinds and unzips• Free activated RNA nucleotides pair up with exposed bases from one strand• Forms sugar-phosphate backbone• Single stranded molecule – mRNA (messenger RNA ) leaves nucleus• Free amino acids and transfer RNA (tRNA ) in cytoplasm. Each tRNA bonds with a particular amino acid• mRNA attaches to ribosome small subunit and codon exposed to the large subunit (first 3 bases always AUG) ALBIO9700/2006JK
  • 5. • tRNA molecule with complementary anticodon forms hydrogen bonds. This tRNA has the amino acid attached to it• A second tRNA (bringing a different amino acid) bonds with the next 3 exposed bases. The 2 amino acids are held closely together and peptide bond is formed between them (reaction catalysed by peptidyl transferase – found in small subunit of ribosome)• Ribosome moves along mRNA ‘reading’ next 3 bases. Several ribosomes work on the same mRNA strand at the same time (polyribosomes ). First tRNA leaves as the third one joins to the second one• Polypeptide chain continues to grow until a ‘stop’ codon (UAA, UAG or UGA) is exposed on the ribosome ALBIO9700/2006JK
  • 6. ALBIO9700/2006JK
  • 7. ALBIO9700/2006JK
  • 8. Genes and genome• Gene – a part of a DNA molecule which codes for just one polypeptide. One DNA molecule contains many genes.• Genome – total set of genes in a cell/total information in one cell/genetic code of organism ALBIO9700/2006JK
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  • 11. ALBIO9700/2006JK

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