6.1.3 Griffith and Transformation

Question 1

note

Answer 1

• Review: In the 1940’s George Beadle and Edward Tatum demonstrated that genes and enzymes were linked. They coined a phrase, “one gene one enzyme,” which has since been modified to “one gene one polypeptide.”
  • In 1928 Frederick Griffith performed a series of experiments with surprising conclusions. Griffith was working with two strains of Pneumococcus bacteria. The smooth (S) strain was known to be virulent, or deadly. The rough (R) strain was avirulent, or not lethal.

Question 2

Frederick Griffith

Answer 2

• worked with two strains of Pneumoccous sp. bacteria. When grown on agar, the type (R) strain produced colonies with a rough surface and the type (S) strain
  produced smooth colonies. When the (R) strain was injected into mice it had no effect. When the (S) strain was injected, the mice died.
• When the type (S) strain is heated and then injected, the mice live. Heating causes some chemical change that makes the pathogenic (S) strain harmless.
• When a mixture of heat-killed (S) cells and living (R) cells are injected into mice, the mice die. An analysis of blood samples taken from the mice reveals live (S) strains.
• Griffith concluded that a substance present in the heat-killed (S) strain transformedthe living (R) strain into (S) bacteria.
• The transforming substance was thought to be the genetic material, still unidentified at this point

Question 3

Frederick Griffith designed a series of experiments to determine

Answer 3

• if a chemical from the pathogenic bacteria could be transferred to nonpathogenic bacteria, making them pathogenic

Question 4

True or false?
Griffith proved that the transfer of DNA between heat-killed S strain to live R strain caused the transformation of the R strain into a lethal form.

Answer 4

• false

Question 5

Beadle and Tatum coined the phrase, “one gene, one enzyme.” The statement has since been changed to

Answer 5

• “one gene, one polypeptide.”

Question 6

In Griffith’s experiment

Answer 6

• heat-killed S strain resulted in a live mouse

Question 7

Based on Griffith’s experimental results, a logical next experiment would be to

Answer 7

• isolate chemicals from the heat-killed pathogenic bacteria and try to transform live nonpathogenic bacteria with each chemical