Post on 02-Dec-2014
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Genetics of Viruses & Bacteria
Chapter 18
VIRUSES
Viral StructureGenetic material & Protein coat
Simplified Viral Reproduction
The Lytic Cycle
Lytic and Lysogenic Cycles
Classes of Animal Viruses
Reproductive Cycles: Enveloped Virus
HIV
Emerging VirusesViruses that make a sudden appearance – they emerge and get the attention of the medical community
Not new – but have evolved and expanded their range/ host
Many come from tropics
Ebola Virus Hantavirus
PrionsInfections proteinsMisfolded protein that is normally present Misfolded protein converts normal proteins
Example – Mad Cow Disease
BACTERIA
Bacterial Genome
• Circular DNA
• No introns
• Replication– Begins at origin– Works its way around – Result – 2 circles– Happens prior to binary
fission
• Small circular pieces of DNA outside of bacterial genome
• Self-replicating
• Used in DNA technology to introduce foreign DNA into bacteria
Plasmids
Genetic Recombination in Bacteria
• Transformation– Uptake of naked DNA from environment
• Conjugation– Transfer of DNA from one bacterial cell to another– Sex pili
• Transduction– Transfer of DNA from bacteriophage to bacteria
(bacteriophage got DNA from previous host cell)
Detecting Genetic Recombination
Transduction (Layer 1)
Transduction (Layer 2)
Transduction (Layer 3)
Transduction (Layer 4)
Bacterial mating (Conjugation)
Conjugation and recombination in E. coli (Layer 1)
Conjugation and recombination in E. coli (Layer 2)
Conjugation and recombination in E. coli (Layer 3)
Conjugation and recombination in E. coli (Layer 4)
Transposons (Insertion Sequences)
• “Jumping genes”• Code for enzyme that copies and moves the transposon• Inverted repeats• May cause mutation if inserted within coding seqence
Composite Transposon
• Includes genes for insertion + functional gene– Ex: antibiotic resistance gene
Regulation of a Metabolic Pathway
Operon: on/ off switch for prokaryotic genes• trp operon - represses enzymes
– In absence of tryptophan• Operon is on• Inactive repressor
– In presence of tryptophan• Operon is off• Tryptophan activates repressor which binds operator
lac operon - Inducible Enzymes• In absence of lactose, no enzymes made• In presence of lactose,
– Lactose binds and inactivates the repressor– Enzymes to digest lactose are made
Eukaryotic Genomes
Chapter 19
Eukaryotic DNA
• Linear
• Levels of packing – Ex: chromatin, chromosomes
• Includes introns
Levels of Packing Eukaryotic DNA
Types of Repetitive DNA
Effect of Transposons
Retrotransposons
Gene regulation in eukaryotic cells
• DNA methylation
• Histone acetylation
• RNA processing
• Transport to cytoplasm
• Translation
• Protein folding
• Transport to destination
• Degradation of protein
Transcription of eukaryotic genes• Introns and exons - exons expressed• Cap and tail added
Alternate RNA Splicing
Protein degradation by a proteostome
Oncogenes & Proto-oncogenes
Signaling pathways that regulate cell growth
Development of colorectal cancer• Multiple mutations lead to carcinoma
– Loss APC gene– Activation of ras oncogene– Loss of tumor-suppressor gene DCC– Loss of tumor-suppressor gene p53– More mutations