1. Chapter 6 Microbial 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. Replication Fork 1 解旋酶打开 DNA 双螺旋

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

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

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

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

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

29. Transformation

30. Conjugation in E. coli

31. Conjugation continued…