The Living World 8th Edition by George Johnson

تمرين 12

In his experiments, Frederick Griffith found that
A) hereditary information within a cell cannot be changed.
B) hereditary information can be added to cells from other cells.
C) mice infected with live R strains die.
D) mice infected with heat-killed S strains die.
The work by Griffith provided the first evidence of transformation. Review the four experiments outlined in figure 11.1. Predict the likely outcome for the following variations on this classic research. Mice are infected with
A) heat-killed pathogenic and heat-killed nonpathogenic bacteria.
B) heat-killed pathogenic and live nonpathogenic bacteria in the presence of an enzyme that digests proteins (proteases).
C) heat-killed pathogenic and live nonpathogenic bacteria in the presence of an enzyme that digests DNA (endonuclease).
Figure 11.1 How Griffith discovered transformation.
Transformation, the movement of a gene from one organism to another, provided some of the key evidence that DNA is the genetic material. Griffith found that extracts of dead pathogenic strains of the bacterium Streptococcus pneumoniae can "transform" live harmless strains into live pathogenic strains.