Genetics of Microorganisms

How are genetic modifications transmitted to offspring?

incorporation of exogenous genetic recombination, or mutation (change in nucleotide order)

Functions of viral genome

has entire viral genetic info, makes infectivity, can self-replicate if nothing else present

pathogenicity vs virulence

patho - ability to cause disease
virulence - degree of aggressiveness

Mutation

stable alteration on genes, constantly transmitted to offspring

Spontaneous mutation

appears normal environmental conditions without the intervention of a discernable factor

Induced mutation

occurs under the action of mutagen factors (physical or chemical)

Point mutation

alteration of a single nucleotide/codon

Errors that cause mutation

errors in nuclei acid replication, transcription/translation

2 classes of mutations

1. following # of affected nucleotide sequences
2. following type of occurrence

Revertant

mutations can be reversible→ Return to original genotype

Recombination

acquirement of exogenous genetic material thru segment exchange bw diff viruses of same host

structural homology is mandatory bw

different DNAs (not dna and rna)

Intramolecular recombination - stages

- joining, breaking (polymerases) and assembling of homologous sequences
- resulting recombinant

Steps of recombination (virus)

1. intramolecular recombination
2. reassortment of genome

Bacterial DNA replication

synthesis of new, identical DNA molecules

Bacterial variability

behavioral modification of bacterial cell or of its descendants

Phenotypical vs genotypical bacterial variants

pheno - adaptive changes, not hereditary, genome not affected
geno - permanent genetic material change, hereditary

Transfer mechanisms of bacterial genetic material - transformation stage

bacteria accepts free DNA from another bacteria/source

Steps of transfer mechanism of bacterial genetic material

1. transformation
2. transfer mediated by bacteriophages
3. conjugation

Transfer mechanisms of bacterial genetic material - transduction stage

transfer of a gene fragment by a bacteriophage (donor bacteria infected, host DNA damaged, new phage particles release + infect)

Transfer mechanisms of bacterial genetic material - conjugation stage

transfer of genetic material from donor bacteria through a mating process (direct contact between the two cells), plasmids + chromosomes transferred

Essential vs accessory genes (bacteria)

essential - in bacterial chromosome
accessory - extrachromosomal (plasmids, transposons + insertion elements)

Plasmids

extrachromosomal, replicate independently, genetic info not essential for bacterial life

Autonomous replication of plasmids

'rolling circle', ori is origin of replication (DNA unwinds), replication is bidirectional w/ enzymes

What is fertility factor and how is it transmitted? (plasmids)

F - gene for sexual pili
transmission for F+ to F- bacteria (+ recombination)

What is R in plasmids

has genes that resist ATB

What is Col in plasmids

encoded colicines (enzymes that kill other bacteria)

Plasmids can be easily modified using

restriction enzymes (gene deletions or insertions)

Transposon

carries genes that confer new functions

Insertion elements

small, carries genes for transposition for prokaryotic cells (used in IS fingerprinting)

What do extrachromosomal elements encode?

- resistance to antibacterials
- synthesis of antimicrobials + colonization factors + hemolysins etc
- enzymes

Detection of NA steps

1. harvesting
2. DNA/RNA extraction
3. gene amplification

Types of PCR

simple vs multiplex (by # genes)
classic - size of amplification products must be diff
real-time (qPCR)- diff fluorophores for each amplified product type
qualitative - gel electrophoresis

What are safe, stable, have low toxicity and cell type specificity?

viral vectors

Advantages and disadvantages of viral vectors

adv - safe, low toxicity, stable, has cell type specificity, help identification
dis - short-lived, immune response, multigene disorders