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transcription and rna



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  • 1. TRANSCRIPTION & RNASDKFebruary 16, 2013
  • 2. Proteins/ Gene Expression• Proteins make up all living materials
  • 3. • Proteins are composed of amino acids – there are 20different amino acids• Different proteins are made by combining these 20amino acids in different combinations
  • 4. • Proteins are manufactured in the ribosomes under thestrict control and order of DNA.• The DNA language is made up of letters which areATGCATATGGAATCAG• These letters forms Words• ATC GCA GGA AUU AUG• These words make sentences•
  • 5. Protein Synthesis
  • 6. DNA, Transcription and Protein Synthesis• DNA contains the genetic information to make aminoacids•Amino acids combine to make proteins• These proteins determine the physical traits of anorganism and control cellular functions.• Proteins do everything, and DNA gets all the credit!
  • 7. • Transcription is the Reading of the DNA andChanging the code to mRNA.• Translation is changing the mRNA into a trait byUsing tRNA to interpret the mRNA.Transcription & Translation
  • 8. • DNA has regions of coding and non-coding.The regions of DNA that code for proteins or traitsare called EXONS, while the regions that do not codefor proteins are called INTRONS.Introns & Exons
  • 9. Making a Protein—Transcription•First Step: Copying of genetic information from DNA to RNAcalled Transcription•Part of DNA temporarily unzips and is used as a template toassemble complementary nucleotides into messenger RNA(mRNA).
  • 10. • Transcription occurs inside the nucleus in a twostep sequence of events.– Pre-mRNA includes both introns and exons for thegene.– mRNA is only the coding portion (exons).• Translation occurs in the cytoplasm at theribosomes.– Reminder: The are three (3) types of RNA• Messenager (mRNA)• Transfer (tRNA)• Ribsomal (rRNA)Site of Transcription&Translation
  • 11. Process of TranscriptionTranscription- process that makes mRNA from DNA1. DNA unzips into 2 separate strandsA. DNA Helicase is the enzyme that breaks H-bond2. Free floating RNA NITROGEN BASES in the nucleus pair upw/unzipped DNA NITROGEN BASES:A. Cytosine(C) pairs with Guanine(G)* (G) with (C)B. Uracil(U) pairs with Adenine(A)* (A) with (U)C. Thymine (T) pairs with Adenine (A)
  • 12. 3. After all the pairing is done:• a single strand of RNA hasbeen produced.4. Genetic code from DNA istransferred to mRNA5. The code obtained from DNAlets the mRNA know whichamino acids to pick up:• code is a set of 3nitrogen bases = Codon
  • 13. A U G G G C U U A A A G C A G U G C A C G U UThis is a molecule of messenger RNA.It was made in the nucleus bytranscription from aDNA molecule.mRNA moleculecodonMessenger RNA
  • 14. A U G G G C U U A A A G C A G U G C A C G U UA ribosome on the rough endoplasmicreticulum attaches to the mRNAmolecule.ribosomeRibosome
  • 15. A U G G G C U U A A A G C A G U G C A C G U UIt brings an amino acid to the first threebases (codon) on the mRNA.tRNA moleculeanticodonU A CA transfer RNA molecule arrives.The three unpaired bases (anticodon)on the tRNA link up with the codon.Transfer RNA
  • 16. A U G G G C U U A A A G C A G U G C A C G U UAnother tRNA molecule comes intoplace, bringing a second amino acid.U A CC C GIts anticodon links up with the secondcodon on the mRNA.Transfer RNA
  • 17. A U G G G C U U A A A G C A G U G C A C G U UA peptide bond forms between thetwo amino acids.Peptide bondC C GU A CTransfer RNA
  • 18. A U G G G C U U A A A G C A G U G C A C G U UThe first tRNA molecule releases its aminoacid and moves off into the cytoplasm.C C GU A CTransfer RNA
  • 19. A U G G G C U U A A A G C A G U G C A C G U UC C GThe ribosome moves along the mRNA tothe next codon.Transfer RNA
  • 20. A U G G G C U U A A A G C A G U G C A C G U UAnother tRNA molecule bringsthe next amino acid into place.C C GA A U
  • 21. A U G G G C U U A A A G C A G U G C A C G U UA peptide bond joins the secondand third amino acids to form apolypeptide chain.C C G C C GPolypeptide chain
  • 22. A U G G G C U U A A A G C A G U G C A C G U UThe polypeptide chain gets longer.G U CA C GThe process continues.This continues until a termination(stop) codon is reached.The polypeptide is then complete.Termination (stop) codon
  • 23. DNA and Protein Synthesis - Summary
  • 24. Use one of the codon charts on the next page to find the amino acidsequence coded for by the following mRNA strands.CAC/CCA/UGG/UGA___________/___________/___________/____________AUG/AAC/GAC/UAA___________/___________/___________/____________
  • 25. CAC/CCA/UGG/UGA___________/___________/___________/____________Histidine1stBase2ndBase3rdBaseProline Tryptophan Stop
  • 26. AUG/AAC/GAC/UAA___________/___________/___________/____________Methionine Asparagine Aspartic Acid Stop
  • 27. DNA and MutationsMutations are any changes that take place in DNA:• Can be spontaneous or caused by mutagens• ex: Chemicals, high temperatures, UV light,radiation• Can change the genetic code, and be replicatedwhen forming new body cells.• In sex cells, can be passed on to offspring.
  • 28. DNA and Mutations – Lets looks at different mutationsTHE DOG BIT THE CAT
  • 29. DNA and Mutations - SubstitutionTHE DOG BIT THE CAT• Substitution - Replace just one letter:THE DOG BIT THE CAR
  • 30. DNA and Mutations - DeletionTHE DOG BIT THE CATDeletion: Delete just one letter (T):THE DOG BIT HEC AT
  • 31. DNA and Mutations-InsertionsTHE DOG BIT THE CAT• Insertion - Add just one letter (E):THE DOE GBI TTH ECA T