DNA structure and history

Question 1

virulent strain that leads to death in mice
leads to smooth colony

Answer 1

S strain

Question 2

benign strain (nonvirulent), mice don’t get sick
leads to rough colony

Answer 2

R strain

Question 3

difference between S and R strains

Answer 3

R lacks protective polysaccharide capsule

Question 4

what happens when live S is injected into mice in Griffith’s experiment

Answer 4

mice get sick and die

Question 5

what happens when live R is injected into mice in Griffith’s experiment

Answer 5

mice stay healthy

Question 6

what happens when heat killed S is injected into mice in Griffith’s experiment

Answer 6

mice stay healthy

Question 7

what happened when mixture of heat killed S and live R were injected into mice in Griffith’s experiment

Answer 7

mice got sick and died

Question 8

what did Griffith’s autopsy find in mice who died with heat killed S + live R

Answer 8

blood was full of live S bacteria, no R bacteria

Question 9

something from heat killed S bacteria got into the live R strain of bacteria and transformed them to virulent S bacteria
most scientists ignored this

Answer 9

Griffith’s conclusion

Question 10

same as Griffith’s experiment but no mice due to criticism from others who said Griffith’s results were caused by something in the mice

Answer 10

Alloway experiment

Question 11

Alloway: in test tube, incubated mixture of heat killed S with live R
incubated overnight and checked under microscope next day RESULT

Answer 11

only S bacteria

Question 12

since transformation of R to S occurred in a test tube without need to inject bacteria into mice and since only thing that is known to have the ability to transform to living things:
live bacteria somehow obtained genetic material form dead S

Answer 12

Alloway’s conclusion

Question 13

Avery et al: same experiments but no S bacteria
in test tube incubated with DNA extracted from heat killed S with live R
incubated overnight and checked under microscope next day
RESULT

Answer 13

all R bacteria turned into S bacteria

Question 14

DNA led to transformation of R bacteria into S bacteria
therefore, DNA must be the genetic materia

Answer 14

Avery et al conclusion

Question 15

when DNA was extracted, wasn’t a clean extraction, may have pulled proteins also

Answer 15

criticism of Avery et al experiment

Question 16

used to inject phage

Answer 16

bacterial phage