Question

1. When Griffiths performed his experiment to show that genetic material can be transferred from one bacterium to another, why did he use a living type IIR strain and a heat-killed type IIIS strain? What type of bacterium was recovered from the dead mice after the mixture of living type IIR and heat-killed type IIIS was injected? Also, specifically include a discussion on mutation versus transformation to change the characteristics of a bacterium.

2. Describe the process by which tRNAs are charged with an amino acid. How is it possible that a specific tRNA will only be bound to a very particular amino acid, and that a different tRNA will also only be bound to a particular amino acid that is different from the first? Provide details on each component involved and of how the recognition is achieved. I am not asking for information about the energetics of the process, just about the specificity of the process.

Answer 1

1. Griffiths used living R strain and heat killed S strain in order to confirm that the bacteria survives in the presence of rough strain and heat killed smooth strain which has lost its virulence after being heated. But contradictory to his thought, the bacteria died.

Later it was recovered that heat killed smooth strain has passed on its virulence factors to rough strain and rough strain has now become virulent and therefore the mice died.

Mutation and transformation both are processes which can lead to genetic changes in bacteria. But mutation is a very non-targeted approach. We try to make mutations on a specific location but we fail to do so but transformation is a targeted approach. We can insert any gene in bacteria which we want to by the process of transformation.

GRIFFITH'S EXPERIMENT Streptococcus preumoniae nough (R) staca Lawulent) smooth (8) strain (uiculent) R + mice Mice alive S + mice - Mice died heated os + mice — Mice aline Rt heated & + mice Mice died isolated

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