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Genes and How They Work

Genes and How They Work. Computer Filename: genes1.ppt Developed by Hugh B. Fackrell. Overview. Genes are composed of DNA within the chromosome Genes code for proteins DNA is transcripted into RNA RNA is translated into protein by ribosomes Genes regulated by control of RNA production.

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Genes and How They Work

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  1. Genes and How They Work Computer Filename: genes1.ppt Developed by Hugh B. Fackrell

  2. Overview • Genes are composed of DNA within the chromosome • Genes code for proteins • DNA is transcripted into RNA • RNA is translated into protein by ribosomes • Genes regulated by control of RNA production

  3. Lecture Outline • Genetic Code • Gene Expression transcription translation • Protein Synthesis • Gene Regulation • Gene Architecture Genes and How They Work

  4. Concepts from OAC • Structure & Function of DNA & RNA • Genetic code • Transcription & translation • Protein synthesis • Gene Regulation: operators, promotors , repressors

  5. Background Terms & Concepts • Structure of DNA & RNA • Ribosomes • Enzymes • Structure of Eukaryotic chromosomes

  6. The Genetic Code • Genetic information is stored in DNA sequences found in • Chromosomes • Mitochondria: 16 KB, 13 genes • Chloroplasts: 120-160 KB, 120 genes

  7. Structure of the Genetic Code • DNA : sequences of four nucleotides A,T,G,C • CODONS : blueprint for the polypeptide • Start & Stop Signals: Where to read the blueprint • Regulatory Sequences: When to read the blueprint • promotors • operators • enhancers

  8. CODONS • sequences of three adjacent nucleotides that code for one amino acid or polypeptide termination • 64 codons encrypt of ~ 20 amino acids • degenerate RNA: ACU, ACC,ACA, ACG threonine • degenerate DNA: TGA, TGG,TGT, TGC threonine

  9. Start Codon • RNA: AUG • DNA: TAC • also codes for methionine

  10. Stop Codon • Nonsense Codons • RNA: UAA,UAG,UGA • DNA: ATT, ATC, ACT

  11. Alternate Genetic Codes Sequence Chromosome Mitochondrion TGA Stop Trypt ATA Isoleucine Methionine AGA Arginine Stop AGG Arginine Stop

  12. Interpreting the Genetic Code • Two step process : • Transcription DNA --> RNA • Translation RNA--> protein

  13. RNA • Ribosomal RNA • Transfer RNA • Messenger RNA

  14. Ribosomal RNA • called rRNA • found in Ribosomes • probably catalytic site • provides site for protein assembly • ribosomal structure different in eukaryotes and prokaryotes

  15. Prokaryotic Ribosomal RNA • large subunit 5s(120), 23s (2900) • Small subunit 16s (1540)

  16. Eukaryotic Ribosomal RNA • Large subunit 5s(120) 28s (4700) 5.8s (160) • Small subunit 18s(1900) Ribosomal RNA 18 S 5.8 S 28 S Transcribed Spacer RNA

  17. Ribosomal RNA

  18. Transfer RNA • called tRNA • Smaller than mRNA or rRNA • found in cytoplasm • 40 different kinds of tRNA • transports amino acids to ribosome • positions amino acids on elongating polypeptide

  19. tRNA

  20. Messenger RNA • called mRNA • long single strand of RNA • copy of the DNA to be decoded • transfers information from the nucleus to the cytoplasm for decoding

  21. Transcription Production of an RNA copy of the gene • occurs in nucleus of eukaryotes • cytoplasm of prokaryotes • DNA unravels- single strand • RNA Polymerase binds to Promotor site • Reads from start sequence(TAC) • assembles complementary single strand of RNA (primary RNA) • Disengages when reaches stop codon

  22. RNA being read from DNA

  23. Prokaryotic Transcription and Translation

  24. Antibody Structure

  25. Eukaryotic Transcription & Translation

  26. Intron Splicing • Regulated at DNA level by restriction endonucleases • Regulated at RNA level by SPLICEOSOMES • GU....AG sequences • thalassemia syndromes

  27. Splicing of DNA

  28. Gene Rearrangement & Processing

  29. mRNA Splicing

  30. DNA Loops

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