Gene Expression: From Genes to Proteins

Transcription

1 The Flow of Genetic Information Gene Expression: From Genes to Proteins Chapter 9 Central Dogma in Molecular Biology molecule Gene 1 Strand to be transcribed Gene 2 Gene 3 strand Codon

2 : Polymerase transcribes into nucleotides Strand to be transcribed polymerase A T C C A A T C A U C C A A U T A G G T Direction of transcription T A Template Strand of Start Stop Newly made strand of a gene Promoter polymerase of gene Terminator 1 Initiation Codon 2 Elongation 3 Termination Growing Completed polymerase

3 9.4 The Flow of Genetic Information Modification: Splicing, 5 Cap and 3 Tail Cap Exon Intron Exon Intron Exon Addition of cap and tail pre- processing Cell Cytoplasm Nucleus transcript with cap and tail Introns removed Exons spliced together Tail Coding sequence Nucleus Cytoplasm Strand to be transcribed of a gene polymerase 1 is transcribed from a template. Enzyme 2 Each amino acid attaches to its proper t with the help of a specific enzyme and ATP. t ATP Initiator t Start Codon Large Small 3 Initiation of polypeptide synthesis The, the first t, and the sub-units come together. Start Stop Growing polypeptide New peptide bond forming 4 Elongation A succession of ts add their amino acids to the polypeptide chain as the is moved through the ribosome, one at a time. Met Lys Phe Stop 5 Termination The ribosome recognizes a stop. The polypeptide is terminated and released.

4 t Transfer Amino Acids Commonly Found in Proteins attachment site Hydrogen bond polynucleotide chain An Amino Acid Amino Acids are linked through Peptide Bonds Amino group Carboxyl group 1 2 Peptide bond

5 The Genetic Code Ribosome t-binding sites Large binding site Small Table 10.5 Growing polypeptide Next amino acid to be added to polypeptide Initiator t Met P site Met Large A site t 1 Start Small 2

6 Amino acid Amino acid P site A site P site A site 1 Codon recognition 1 Codon recognition 2 Peptide bond formation New peptide bond 2 Peptide bond formation 3 Translocation Amino acid of a gene P site A site polymerase 1 is transcribed from a template. 1 Codon recognition Enzyme 2 Each amino acid attaches to its proper t with the help of a specific enzyme and ATP. t ATP movement Initiator t Start Codon Large Small 3 Initiation of polypeptide synthesis The, the first t, and the sub-units come together. Stop Growing polypeptide New peptide bond forming New peptide bond 2 Peptide bond formation 4 Elongation A succession of ts add their amino acids to the polypeptide chain as the is moved through the ribosome, one at a time. 3 Translocation Stop 5 Termination The ribosome recognizes a stop. The polypeptide is terminated and released.

7 Termination Several Antibiotics inhibit Bacterial Tetracyclin: Initiation of Streptomycin: disrupts -t interaction Chloramphenicol: inhibits peptide bond Erythromycin: binds to large of ribosome Figure : Multiple Copies of a Protein Are Made Simultaneously Levels of Protein Structure

8 Misfolding of Protein Impairs Function One Protein, Multiple Conformations Prions: A Protein Folding Disorder Protein Processing, Sorting, and Transport Nucleus Ribosomes Lumen of ER Membrane Lysosome ER Proteins Vesicle Golgi apparatus Plasma membrane Proteins Secretory granule Cytoplasm Secretion

9 Some Biological Functions of Proteins