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Name: Josh
Status: Student
Grade:  9-12
Location: PA
Country: United States
Date: November 2007


Question:
If Griffith used heat to kill the bacteria in his experiment, wouldn't the DNA be denatured and therefore would not affect the mice?



Replies:
The smooth bacteria were killed by the heat. He did not heat kill the rough bacteria. when DNA is denatured it isn't the same thing as denaturing protein. Denaturing disrupts hydrogen bonds holding the molecule together. In proteins this destroys the tertiary structure (3D shape) which destroys its function. In DNA this breaks the two strands of the double helix apart into single strands. When Griffith mixed the two types of bacteria together in the same tube, the rough bacteria were able to scavenge the smooth bacteria's DNA and take portions into its own DNA by recombination. In other words, the rough bacteria took in a portion of the smooth DNA and exchanged it with its own DNA for that portion. This gave it a gene it didn't have on its own and allowed it to survive the mouse's immune system so it wasn't killed. This process of one bacteria taking in genes from its surroundings is called transformation.

vanhoeck



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