Question

You and a classmate are discussing early experiments in genetics, and you state that Avery, MacLeod, and McCarty provided the first evidence that DNA carries genetic information. Your classmate argues that Griffith was the first to demonstrate this. Which statement best defends your argument?

1) Although Griffith first demonstrated transformation, Avery, MacLeod, and McCarty provided evidence that DNA rather than protein or RNA was the transforming agent.
2) Avery, MacLeod, and McCarty worked with purified DNA extracts while Griffith worked with bacterial strains.
3) Enzymes were used in the experiments carried out by Avery, MacLeod, and McCarty while Griffith transformed cells chemically or by using heat.
4) Because Avery, MacLeod, and McCarty did their experiments after those done by Griffith, they had much more information regarding the structure and function of DNA.
5) DNA used by Avery, MacLeod and McCarty was extracted solely from transformed strains of pneumococci, while Griffith used native pneunococcal strains.

Answer 1

The experiments by Avery, MacLeod, and McCarty showed that DNA was the transforming principle because transformation did not occur when DNA was specifically degraded, providing direct evidence of DNA as the carrier of genetic information.

Step-by-step explanation:

Although Frederick Griffith first demonstrated the phenomenon of transformation, it was the experiments by Oswald Avery, Colin MacLeod, and Maclyn McCarty that provided evidence that DNA carries genetic information. While Griffith's work identified that a transforming principle caused non-virulent bacteria to become virulent, Avery, MacLeod, and McCarty went a step further by purifying the different compounds from the bacteria and using enzymes that specifically degraded each component. Their findings showed that only when DNA was destroyed, the mixture lost its ability to transform the R strain of pneumococcus, indicating that DNA was the transforming principle and thus the carrier of genetic information.