1 / 32

Chapter 6 Microbial Genetics

Chapter 6 Microbial Genetics. Structure and Function of Genetic Materials. DNA & RNA DNA=deoxyribonucleic acid RNA=ribonucleic acid Basic building blocks: Nucleotides Phosphate group Pentose sugar Nitrogenous base. Structure of DNA. Double stranded (double helix) Chains of nucleotides

reina
Download Presentation

Chapter 6 Microbial Genetics

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. Chapter 6Microbial Genetics

  2. Structure and Function of Genetic Materials DNA & RNA DNA=deoxyribonucleic acid RNA=ribonucleic acid Basic building blocks: Nucleotides Phosphate group Pentose sugar Nitrogenous base

  3. Structure of DNA • Double stranded (double helix) • Chains of nucleotides • 5’ to 3’ (strands are anti-parallel) • Complimentary base pairing • A-T • G-C

  4. DNA Structure Phosphate-P Sugar-blue Bases-ATGC

  5. DNA Replication • Bacteria have closed, circular DNA • Genome: genetic material in an organism • E. coli • 4 million base pairs • 1 mm long (over 1000 times larger that actual bacterial cell. How it can be put into a cell? • DNA takes up around 10% of cell volume

  6. DNA Replication occurs at the replication fork • 5’ to 3 ‘ • DNA helicase-unzips + parental DNA strand that is used as a template • Leading stand (5’ to 3’-continuous) • DNA polymerase-joins growing DNA strand after nucleotides are aligned (complimentary) • Lagging strand (5’ to 3’-not continuous) • RNA polymerase (makes short RNA primer) • DNA polymerase (extends RNA primer then digests RNA primer and replaces it with DNA) • DNA ligase (seals Okazaki fragments-the newly formed DNA fragments)

  7. 解旋酶打开DNA双螺旋 Replication Fork 1

  8. Protein Synthesis DNA------- mRNA------ protein transcription translation Central Dogma(中心法则) of Molecular Genetics

  9. Transcription • One strand of DNA used as a template to make a complimentary strand of mRNA • Promoter/RNA polymerase/termination site/5’ to 3’ • Ways in which RNA & DNA differ: • RNA is ss • RNA sugar is ribose • Base pairing-A-U

  10. The structure of a bacterial gene I. Single gene transcript Translational end Transcription start site Coding sequence TAA ATG hisG transcript Transcriptional terminator Ribosome binding site/ translational start (ATG) Promoter

  11. Multigene bacterial operon Translational end Transcription start site TAA ATG TAA hisG hisH transcript -One promoter, one transcriptional stop; multiple translational starts and stops

  12. Transcription

  13. Types of RNA • Three types: • mRNA: messenger RNA • Contains 3 bases ( codon) • rRNA: ribosomal RNA • Comprises the 70 S ribosome • tRNA: transfer RNA • Transfers amino acids to ribosomes for protein synthesis • Contains the anticodon (3 base sequence that is complimentary to codon on mRNA)

  14. Genetic Code • DNA: triplet code • mRNA: codon (complimentary to triplet code of DNA) • tRNA: anticodon (complimentary to codon)

  15. Genetic Code • Codons: code for the production of a specific amino acid • 20 amino acids • 3 base code • Degenerative: more than 1 codon codes for an amino acid • Universal: in all living organisms

  16. Genetic Code

  17. Translation • Three parts: • Initiation-start codon (AUG) • Elongation-ribosome moves along mRNA • Termination: stop codon reached/polypeptide released and new protein forms • rRNA=subunits that form the 70 S ribosomes (protein synthesis occurs here) • tRNA=transfers amino acids to ribosomes for protein synthesis)

  18. Translation

  19. Translation

  20. Translation

  21. Translation

  22. Mutations • Changes in base sequence of DNA/lethal and inheritable • Can be: • Harmful • Lethal • Helpful • Silent

  23. Normal DNA/Missense Mutation

  24. Nonsense Mutation/Frameshift Mutation

  25. Genetic Transfer in Bacteria • Genetic transfer results in genetic variation • Genetic variation is needed for evolution • Three ways: • Transformation: genes transferred from one bacterium to another as “naked” DNA • Conjugation: plasmids transferred 1 bacteria to another via a pilus • Transduction: DNA transferred from 1 bacteria to another by a virus

  26. Transduction by a bacteriophage

  27. Generalized Transduction • Infection of Donor • Phage replication and degradation of host DNA • Assembly of phages particles • Release of phage • Infection of recipient • Homologous recombination Potentially any donor gene can be transferred

  28. Transformation • Steps • Uptake of DNA • Gram + • Gram - • Recombination • Legitimate, homologous or general • recA, recB and recC genes • Significance • Phase variation in Neiseseria • Recombinant DNA technology

  29. Transformation

  30. Conjugation in E. coli

  31. Conjugation continued…

  32. Conjugation continued…

More Related