Genetic transfer and linkage mapping in bacteria: Transformation

Question 1

Transformation definition

Answer 1

Direct uptake of DNA

Question 2

Transformation Experiment by Griffiths/Avery

Answer 2

2 types of Streptococcus pneumoniae - rough (non-pathogenic) + smooth (pathogenic +kill mice)
- Dead S cells do not kill
- Mixing dead S cells with live R cells transform into a smooth phenotype

Avery narrowed down transforming factor is DNA => is the genetic material

Question 3

‘Competent’ cells + the types

Answer 3

Cells capable of taking up DNA
Includes ‘Natural’ and ‘Induced’ competence

Question 4

Induced competence

Answer 4

Most bacteria had to have competence induced with chemicals or an electrical field

Question 5

Pros + Cons of Induced Competence

Answer 5

• Invaluable tool that can introduce a range of genetic information in the form of plasmids, transposons, homologous DNA for gene replacement
• Difficult with large pieces of DNA (>~20kbp)

Question 6

Example of Natural Competence

Answer 6

Streptococcus, Bacillus, etc. have a specialised competence machinery for the import of DNA + thought to be exchanging genes constantly

• DNA is made single stranded upon import then can recombine with recipient chromosome