1. MICROBIAL GENETICS
CHAPTER 7

2. Heredity Diversity in the gene pool is vital Eukaryotes
Mating partners
Random chromosome alignment during Meiosis I
Homologous chromatid recombination events
Prokaryotes
Mutation/ rapid reproduction rates
Lateral gene transfer (Ch.8)

3. Genetic Information Storage
Chromosomal sizes
E. coli 4 x 106 bp
H. sapiens 3 x 109 bp
Microbial gene size ~1000bp
Gene composition - CG rich

4. DNA Structure Double stranded Helical Sugar-phosphate backbone
5’ to 3’ orientation
Base pairs
A-T
C-G

5. DNA Concepts Genes Functional unit encoding a protein or RNA product
Often determine a single characteristic
Units are located at fixed loci along the chromosome
Alleles
Variations in the base sequences of a gene
Their diversity expands the gene pool
Mutations
Alterations in gene sequence which create new alleles
Many chemical and physical causes

6. Information Transfer - Gene Expression

7. DNA Replication 5’ to 3’ nucleotide arrangement Antiparallel strands
ori - origin of replication
DNA Polymerase
Strands elongate at 3’ end
Leading strand versus Lagging strand
DNA Ligase

8. DNA Replication Semi-conservative replication
Both strands are templates

9. Transcription DNA to RNA, also 5’ to 3’
One strand only serves as RNA template
RNA polymerase
Promoter / terminator

10. RNA Types Ribosomal RNA (rRNA)
component of the ribosome along with ribosomal proteins
Messenger RNA (mRNA)
codons dictate the linear arrangement of amino acids in a protein
Transfer RNA (tRNA)
anticodons base pair against codons in mRNA allowing the amino acids they carry to be the correct ones

11. Gene Representation t mRNA Coding/ structural region Promoter
Terminator
Coding/ structural region
mRNA

12. mRNA Variations Eukaryotic Introns transcribed then spliced out
Exon shuffling can occur to create new proteins
Prokaryotic
No introns
Operons speed up protein synthesis

13. Genetic Code – mRNA codons

14. Translation tRNA anticodons
Triplet complementary to the codon in structural gene region
Amino acid links
Covalent attachment of a.a. using ATP energy
Role of ribosomes
Provides environment to allow adjacent a.a’s to form a peptide bond
Anticodon
Amino acid
binding site

15. Protein Synthesis

16. Protein Synthesis

17. Simultaneous Transcription/Translation
No Nuclear membrane in prokaryotes
Ribosomal alignment

18. Visualizing Prokaryotic Coupling of Transcription and Translation

19. Regulation of Metabolism
Feedback Inhibition
Biochemical
Enzyme Induction
Genetic
Enzyme Repression

20. Lac Operon

21. Mutations Genotype Phenotype Point Mutations (Substitutions) Silent
Missense
Nonsense

22. Frameshift Mutations Insertions/Deletions
All triplet codons are altered by one or two base insertions or deletions
Reading Frame
Chromosomal Rearrangements

23. Causes of Mutation Spontaneous versus Induced Chemical mutagens
Radiation Types

24. DNA Repair Defects Human Genetic DNA Repair disorders Genetic diseases
Xeroderma pigmentosum
Werner’s syndrome
Bloom’s syndrome
Progerias
Accelerated aging
Mental retardation
Damage to early neurons

25. Ames Test Detects mutagens S. typhimurium (his-) Rat Liver Extract
90% correlation with animal tests.

26. Ames Test Technique

27. Polymerase Chain Reaction
DNA amplification in vitro
Applications
Forensics
Conservation biology
Diagnostics
PCR protocol