12. Bacterial Genetics Flashcards
(32 cards)
Why would every bacterial mutation be expressed?
They’re haploid
2 methods bacteria use to save genome space?
No introns (=no alternative splicing)
Can use overlapping genes
Example of a bacteria that has linear chromosomes
Vibrio cholerae
What does polycistronic mean? (bacterial mRNA are polycistronic)
RNA contains the sequences of many different proteins (more than one protein)
3 main differences between bacterial and eukaryotic mRNA?
Bacterial have no 5’-cap, no polyA tail, are polycistronic
What do bacterial non-coding regions contain?
Binding sites for proteins that affect transcription
5 things that can cause heritable changes in bacterial genotype?
Mutation
Conjugation
Transformation
Transduction
Genetic engineering
Describe the 3 types of point mutations?
Silent - change in wobble codon, no change in aa
Missense - aa change
Nonsense - introduces STOP codon
3 reasons why we would want to generate strains with novel properties?
- Increase antibiotic production
- Increase heat stability of a protein
- Increase ethanol tolerance of the producing microbe
Easy and hard way of increasing mutation rate? Rate increase?
Hard: use strains deficient in DNA repair enzymes
Easy: Expose microbe to mutagens
10-1000X
4 major classes of mutagens and how they work?
Base analogues - incorporates into DNA like it’s a T but often pairs with a G (5-bromo-uridine)
DNA intercalating agents - intercalates into dsDNA to form bulk lesions -> often repaired INCORRECTLY (ethidium bromide)
Alkylating agents - transfers an alkyl group to the DNA (methylnitrosoguanidine)
Radiation (UV, ionizing - X-ray)
2 conditions that must be met for a heritable change in the genome?
DNA damage NOT repaired completely
Organism survives
What is selective pressure?
A selective mechanism so that only the mutants of interest survive or are easily distinguished from others
3 differences between eukaryotic/prokaryotic gene transfer?
Gene transfer REQUIRED in euk; non-reciprocal in prok
Occurs during MEIOSIS for euk, conjugation/transformation/transduction for prok
Between 2 homologous chromosomes for euk; exogenote/endogenote for prok
What is horizontal gene transfer?
Method that genes are transferred from one mature, independent organism to another
Describe the 2 methods for screening mutants
Positive selection - isolate an antibiotic resistant strain
Negative selection - for loss of function mutants e.g. isolate an auxotroph
Tool used in replica plating?
Replica block covered with velvet surface
How do x-rays cause mutations?
Break phosphodiester backbone in DNA
What is a merozygote
Recipient cell in horizontal gene transfer that is temporarily diploid
4 fates of horizontally transferred DNA in prokaryotes?
- Integrate into recipient genome
- Form partial diploid and replicate
- Form partial diploid and NOT replicate
- Degradation
How does donor DNA get incorporated into host DNA?
Through DNA recominbation
Name of mechanism proposed for the recombination occurring during transformation in some bacteria?
Fox model (non-reciprocal homologous recombination)
Homologous implies___________
evolutionary relatedness (donor and recipient share high degree of sequence familiarity)
Exogenote vs endogenote?
Exogenote = donor DNA
Endogenote = recipient DNA
