1 / 22

Protein Synthesis

Protein Synthesis. Revision. The Genetic Code. A gene is a sequence of bases in DNA that codes for the sequence of amino acids in a polypeptide (protein) The ‘language’ of a gene has only 4 letters - these are? A T C and G. The Genetic Code. The ‘language’ of a protein has 20 letters

vaughn
Download Presentation

Protein Synthesis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Protein Synthesis Revision

  2. The Genetic Code A geneis a sequence of bases in DNA that codes for the sequence of amino acids in a polypeptide (protein) The ‘language’ of a gene has only 4 letters - these are? A T C and G

  3. The Genetic Code The ‘language’ of a protein has 20 letters - these are? The 20 different amino acids that make up proteins

  4. The Genetic Code • If 1 base coded for one amino acid in a protein then, only 4 amino acids could be coded for • If 2 bases coded for one amino acid in a protein then, only 16 amino acids could be coded for • If 3 bases coded for one amino acid in a protein then, 64 amino acids could be coded for – more than enough 41 = 4 42 = 16 43 = 64 The genetic code is a triplet code

  5. The Genetic Code • There are 20 amino acids to be coded for and 64 base triplets to use to code them • Each amino acid has more than one code word – that is the genetic code is degenerate.

  6. The Genetic Code The genetic code is non-overlapping ATTCGAGGCGGT is ‘read’ asATT CGA GGC GGT Each base is a part of only one triplet.

  7. The Genetic Code is: • A triplet code • Degenerate • Non-overlapping • Universal

  8. Protein synthesis • 2 major processes involved • Transcription • Translation

  9. Transcription • The relevant gene in the DNA in the nucleus is ‘copied’ into a molecule of RNA called mRNA or messenger RNA

  10. A G C T A G C T Transcription • DNA double helix unzips as • hydrogen bonds between complementary bases break • and the two polynucleotide strands separate

  11. A G C U A G C T A G C T Transcription • One strand called the sense strand acts as a template, free RNA nucleotides complementary base pair to the exposed bases on this strand by forming hydrogen bonds • RNA polymerase forms sugar-phosphate bonds between nucleotides

  12. A G C U A G C T A G C T Transcription • The mRNA detaches from the sense strand • The two DNA strands join together by complementary base pairing • The DNA molecules winds back up into a helix

  13. Transcription • The sequences of 3 bases on the mRNA coding for amino acids are called CODONS. • Not all the bases in the DNA code for amino acids so the mRNA just transcribed contains non-coding regions known as INTRONS

  14. enzymes Transcription exon intron exon intron exon These introns are removed by enzymes before the mRNA leaves the nucleus This leaves just EXONS or coding regions of mRNA

  15. enzymes Transcription intron intron exon exon exon These introns are removed by enzymes before the mRNA leaves the nucleus This leaves just EXONS or coding regions of mRNA

  16. mRNA nucleus ribosome Transcription to translation Following the removal of introns the mRNA moves out through a nuclear pore and attaches to a ribosome

  17. aa2 aa1 tRNA tRNA GGG UAC anticodon start codon stop codon AUG CCC GGG CGC ACA CGU UUC UGA Translation

  18. peptide bond formed aa2 aa1 tRNA tRNA GGG UAC AUG CCC GGG CGC ACA CGU UUC UGA

  19. aa2 tRNA tRNA GGG UAC AUG CCC GGG CGC ACA CGU UUC UGA aa1 ‘empty’ tRNA leaves to pick up another specific amino acid

  20. aa3 aa2 tRNA tRNA CCC GGG AUG CCC GGG CGC ACA CGU UUC UGA aa1 Ribosome moves along mRNA by one codon

  21. peptide bond formed aa3 tRNA tRNA CCC GGG AUG CCC GGG CGC ACA CGU UUC UGA aa2 aa1 ‘empty’ tRNA leaves to pick up another specific amino acid

  22. tRNA aa2 aa4 aa6 aa8 aa1 aa3 aa5 aa7 ACU AUG CCC GGG CGC ACA CGU UUC UGA This process is repeated until the ribosome reads a stop codon

More Related