microbial genetic
TRANSCRIPT
![Page 1: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/1.jpg)
Microbial Genetics
Chapter 8
![Page 2: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/2.jpg)
Structure and Function of Genetic Material DNA & RNA
DNA• deoxyribonucleic acid
RNA• ribonucleic acid
Nucleotides• Phosphate group• Pentose sugar• Nitrogenous base
![Page 3: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/3.jpg)
![Page 4: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/4.jpg)
![Page 5: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/5.jpg)
Structure of DNA
Double stranded (double helix) polymers of nucleotides 5’ to 3’ (strands are anti-parallel) Complimentary Base Pairing
• A - T• G - C
![Page 6: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/6.jpg)
DNA Replication
Bacteria have only 1 chromosome (ccDNA) E. coli
• about 4 million base pairs• 1 mm long (1000 times longer than the cell)• DNA takes up only about 10 % of cells volume
![Page 7: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/7.jpg)
E. coli DNA
1u 1,360u
1ft. 1,360 ft.
![Page 8: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/8.jpg)
DNA Replication occurs at the Replication Fork (5’ to 3’) DNA Helicase 1. Leading Strand ( 5’ to 3’ )
• DNA Polymerase
2. Lagging Strand ( 5’ to 3’)• RNA Polymerase (RNA Primer)• DNA Polymerase (extends primer and digests
RNA)• DNA Ligase
• Okazaki Fragments
![Page 9: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/9.jpg)
![Page 10: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/10.jpg)
Bidirectional replication
Origin of replication
Termination site
![Page 11: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/11.jpg)
Protein Synthesis
DNA mRNA Protein
Transcription Translation
Central Dogma of Molecular Genetics
![Page 12: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/12.jpg)
Transcription
One strand of DNA is used as a template to form a complimentary strand of mRNA
mRNA ----> messenger RNA
![Page 13: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/13.jpg)
Transcription
3 ways RNA differs from DNA
Promoter RNA Polymerase Termination Site 5’ to 3’
![Page 14: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/14.jpg)
![Page 15: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/15.jpg)
3 Types of RNA
1. mRNA• Contains the codons
2. rRNA• Ribosomes (70S)
3. tRNA• Transfer amino acids to the ribosomes for
protein synthesis• Anti-codon
![Page 16: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/16.jpg)
Genetic Code
DNA
mRNA
tRNA
Triplet code
codons
anticodons
![Page 17: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/17.jpg)
Genetic Code
Codons code for a specific amino acid 20 amino acids 3 base code - 4 bases ( A,U,G,C ) 64 possible combinations ( 43) Amino acids are coded for by more than one
codon Genetic Code is Degenerative Genetic Code is Universal
![Page 18: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/18.jpg)
![Page 19: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/19.jpg)
Translation
rRNA• ribosomal RNA (forms the ribosomes) (70S)
tRNA• transfer RNA (transfers amino acids to the
ribosomes for protein synthesis)• anticodon
• 3 base sequence that is complimentary to the codon on mRNA
![Page 20: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/20.jpg)
![Page 21: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/21.jpg)
![Page 22: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/22.jpg)
![Page 23: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/23.jpg)
![Page 24: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/24.jpg)
Regulation of Gene Expression
All Genes are not always being expressed
Genes turned on all the time - Constitutive
Other genes can be regulated:• Turned On• Turned Off
![Page 25: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/25.jpg)
lac operon
Lac - Lactose (dissacharide)• Glucose and Galactose
operon - series of structural genes all under the control of a Regulatory Gene
lac operon is normally turned off
lac operon is an Inducible operon
![Page 26: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/26.jpg)
Tryptophan operon
Tryptophan - amino acid operon - series of structural genes all under
the control of a Regulatory Gene
Tryptophan operon is normally turned on
Tryptophan operon is a repressible operon
![Page 27: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/27.jpg)
Mutations - a change in the base sequence of DNA
Mutations can be: 1. Harmful 2. Lethal 3. Beneficial 4. Silent (neutral)
• UUU - Phe• UUC - Phe
![Page 28: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/28.jpg)
Types of Mutations
Normal DNA
![Page 29: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/29.jpg)
Base Substitution MutationC
Missense Mutation
![Page 30: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/30.jpg)
T
Nonsense Mutation
Base Substitution Mutation
![Page 31: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/31.jpg)
Frame Shift Mutation ATG CAT GCA TGC ATT TCC TGC TTA AAA
1. Addition Mutation
AAT GCA TGC ATG CAT TTT CCT GCT TAA
Reading Frame is Shifted
2. Deletion Mutation
TGC ATG CAT GCA TTT CCT GCT TAA
Reading Frame is Shifted
![Page 32: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/32.jpg)
Genetic Transfer in Bacteria
Genetic Transfer - results in Genetic Variation Genetic Variation - is needed for Evolution
3 Ways Genetic Transfer can occur in Bacteria• 1. Transformation
• 2. Cunjugation
• 3. Transduction
![Page 33: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/33.jpg)
Transformation
Genes are transferred from one bacterium to another as “naked” DNA
Frederick Griffith (1928)
![Page 34: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/34.jpg)
Griffith’s Experiment
2 Strains of Streptococcus pneumoniae
• 1. Virulent strain with a capsule - Pneumonia
• 2. Avirulent strain without a capsule - no disease
![Page 35: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/35.jpg)
Griffith’s Experiment
![Page 36: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/36.jpg)
Griffith’s Experiment
![Page 37: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/37.jpg)
Griffith’s Experiment
![Page 38: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/38.jpg)
Griffith’s Experiment
![Page 39: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/39.jpg)
![Page 40: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/40.jpg)
Conjugation
One bacterium passes some DNA (in a plasmid) to another bacterium
![Page 41: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/41.jpg)
Transduction
DNA is transferred from one bacterium to another by a virus
Bacteriophage• virus that only infects bacteria
![Page 42: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/42.jpg)
![Page 43: Microbial Genetic](https://reader033.vdocument.in/reader033/viewer/2022052315/544dcb9baf7959f7138b5127/html5/thumbnails/43.jpg)