* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Transcription & Translation
RNA interference wikipedia , lookup
Bottromycin wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
Molecular cloning wikipedia , lookup
Community fingerprinting wikipedia , lookup
Biochemistry wikipedia , lookup
Promoter (genetics) wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
RNA silencing wikipedia , lookup
Real-time polymerase chain reaction wikipedia , lookup
Molecular evolution wikipedia , lookup
Non-coding DNA wikipedia , lookup
Polyadenylation wikipedia , lookup
Eukaryotic transcription wikipedia , lookup
RNA polymerase II holoenzyme wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Silencer (genetics) wikipedia , lookup
Transcriptional regulation wikipedia , lookup
Point mutation wikipedia , lookup
Gene expression wikipedia , lookup
Non-coding RNA wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Expanded genetic code wikipedia , lookup
Messenger RNA wikipedia , lookup
Deoxyribozyme wikipedia , lookup
THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN A specific gene specifies a polypeptide – The DNA is transcribed into RNA, which is translated into the polypeptide DNA TRANSCRIPTION RNA TRANSLATION Protein Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings CODONS • The “words” of the DNA “language” are triplets of bases called codons – The codons in a gene specify the amino acid sequence of a polypeptide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gene 1 Gene 3 DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Figure 10.7 Amino acid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings CODON TRANSLATION • Virtually all organisms share the same genetic code • 64 Codons total (4 x 4 x 4) • AUG = Start (Met) • 3 Stops • Redundant, but NOT ambiguous Figure 10.8A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • An exercise in translating the genetic code Transcribed strand DNA Transcription RNA Start codon Polypeptide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Translation Stop codon Figure 10.8B Where does RNA come from: TRANSCRIPTION RNA polymerase RNA nucleotide Direction of transcription Template strand of DNA Figure 10.9A Newly made RNA Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings RNA polymerase • In transcription, the DNA helix unzips – Promoter: turns a gene on/off – RNA nucleotides line up along one strand of the DNA following the base-pairing rules – The single-stranded messenger RNA peels away and the DNA strands rejoin Figure 10.9B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA of gene Promoter DNA Initiation Elongation Terminator DNA Area shown in Figure 10.9A Termination Growing RNA Completed RNA RNA polymerase RNA Processing: Splicing Exons & Discarding Introns • Noncoding segments called introns are spliced out Exon Intron Exon Intron Exon DNA Cap RNA transcript with cap and tail • A cap and a tail are added to the ends Transcription Addition of cap and tail Introns removed Tail Exons spliced together mRNA Coding sequence NUCLEUS CYTOPLASM Figure 10.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings TRANSLATION: tRNA helps assemble the polypeptide chain (amino acids) • In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a polypeptide • The process is aided by transfer RNAs Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Figure 10.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other Amino acid attachment site Anticodon Figure 10.11B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Ribosomes build polypeptides Next amino acid to be added to polypeptide Growing polypeptide tRNA molecules P site A site Growing polypeptide Large subunit tRNA P A mRNA mRNA binding site Codons mRNA Small subunit Figure 10.12A-C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • mRNA, a specific tRNA, and the ribosome Large ribosomal subunit Initiator tRNA P site A site Start codon mRNA Small ribosomal subunit 1 Figure 10.13B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 Amino acids are added to the polypeptide chain until a stop Codon is reached • The mRNA moves a codon at a time • A tRNA pairs with each codon, adding an amino acid to the growing polypeptide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Amino acid Polypeptide A site P site Anticodon mRNA 1 Codon recognition mRNA movement Stop codon New peptide bond 3 Translocation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 Peptide bond formation Figure 10.14 Review: The flow of genetic information in the cell is DNARNAprotein • The sequence of codons in DNA spells out the primary structure of a polypeptide – Polypeptides form proteins that cells and organisms use Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Summary of transcription and translation TRANSCRIPTION DNA mRNA RNA polymerase Stage 1 mRNA is transcribed from a DNA template. Amino acid TRANSLATION Enzyme Stage 2 Each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP. tRNA Initiator tRNA mRNA Figure 10.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Anticodon Large ribosomal subunit Start Codon Small ribosomal subunit Stage 3 Initiation of polypeptide synthesis The mRNA, the first tRNA, and the ribosomal subunits come together. New peptide bond forming Growing polypeptide Codons Stage 4 Elongation A succession of tRNAs add their amino acids to the polypeptide chain as the mRNA is moved through the ribosome, one codon at a time. mRNA Polypeptide Stop Codon Figure 10.15 (continued) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stage 5 Termination The ribosome recognizes a stop codon. The polypeptide is terminated and released. Mutations can change the meaning of genes • Mutations are changes in the DNA base sequence – These are caused by errors in DNA replication or by mutagens – The change of a single DNA nucleotide causes sickle-cell disease Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Normal hemoglobin DNA mRNA Mutant hemoglobin DNA mRNA Normal hemoglobin Sickle-cell hemoglobin Glu Val Figure 10.16A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Types of mutations NORMAL GENE mRNA Protein Met Lys Phe Gly Ala Lys Phe Ser Ala BASE SUBSTITUTION Met Missing BASE DELETION Met Lys Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Leu Ala His Figure 10.16B