BGM1004/L02 Bacterial Genetics I Flashcards
What is genetics?
The study of inheritance and manipulation of genetic information
Why do we study genetics? (3)
Improve understanding of how organisms work
Detect and treat diseases
Exploit organisms for benefit of humankind and environment
What genetic approaches existed before DNA manipulation? (2)
Classical genetics
Random mutagenesis, selection and re-assortment of an organism’s characteristic by genetic crosses
What is CRISPR?
Recently developed technology that facilitates in vivo genetic engineering with surgical precision
Why are bacterial genetics studied? (4)
Simple organisms
Exhibit most basic principles of genetics
Easy to manipulate
Short generation times
Why are haploid organisms useful to study? (4)
Easier to identify mutations within cells
Immediate effect on organism
Higher organisms usually diploid/polyploid
Most mutations are recessive
Give 3 Darwinian Principles.
Changes in heritable properties occur randomly
Vertical gene transfer
Natural selection
What did Luria & Delbruck show about bacterial inheritance (1941)?
Inheritance in bacteria was Darwinian
What is gene transfer from bacteria/environment to bacteria called?
Horizontal gene transfer
What did the Griffith experiment (1928) show?
Gene transformation
Heritable properties of a bacterium can be transferred from one to another
What did the Lederberg & Tatum experiment (1946) show?
Conjugation
When 2 strains of E. coli with different traits are mixed, they could isolate progeny with traits from both parents
What did the Zinder & Lederberg experiment (1953) show?
Transduction
Bacterial viruses could carry DNA from one bacterium to another
Name 3 bacterial gene transfer mechanisms.
Transformation
Transduction
Conjugation
Which kind of bacterial colony causes disease?
Smooth (S) colonies
Why do smooth bacterial colonies cause disease?
Not easily recognised by immune system
Why are smooth colonies described as ‘virulent’?
They cause disease
Capsule evades immune system
What happened in the Griffith experiment, when mice were injected with smooth and rough bacteria?
Smooth - mouse dies
Rough - mouse survives
What happened in the Griffith experiment, when mice were injected with live rough and dead smooth bacteria? What does this suggest?
Mouse dies
Rough bacteria undergo horizontal gene transfer to become smooth & virulent
What experiment was completed to show that DNA was the transforming factor in the Griffith experiment?
Protease or RNase was added to culture of R cells
What term describes the appropriate physiological state of bacteria to enable transformation?
Competence
What structure pulls bacteria together during conjugation?
Pilus
What is conjugation mediated by?
Conjugative (or fertility) plasmid
Where is DNA stored in bacteriophages?
Head
What does the function of a bacteriophage tail compare to?
Hypodermic syringe
Why are phages able to complete bacterial transduction?
Mistakes when packaging DNA into phage particles
What do bacteriophages becomes filled with during transduction?
Another host chromosomal DNA or mixture of host and phage DNA
If DNA is related during bacterial transduction, how can it be integrated?
Homologous transduction
