DNA Testing and Chemical Reactions

In this biology tutorial, students conduct an experiment to observe the reaction between banana DNA and diphenylamine, which should result in a color change to black. Initially, the expected color change does not occur, prompting a second test. The final results show a darker color, suggesting a successful reaction, but further tests are needed to confirm the presence of DNA.

What was the purpose of adding diphenylamine to the test tubes with banana DNA?

• To preserve the DNA

• To neutralize the DNA

• To react with DNA and change its color

• To dissolve the DNA

What was the expected color change in the DNA test tubes after boiling for ten minutes?

• Red

• Blue

• Black

• Green

What was the control in the experiment?

• Test tubes with banana DNA

• Test tubes with water

• Test tubes with no DNA

• Test tubes with diphenylamine

What was the actual color observed in the DNA test tubes after the first boiling?

• Olive green

• Black

• White

• Blue

What did the teacher decide to do after observing the unexpected results?

• Increase the boiling time

• Change the chemical used

• Run a second test with more DNA

• Stop the experiment

What was added to the new test tubes for the second test?

• More water

• More diphenylamine

• More control samples

• More banana DNA

What was the result of the second boiling with the new DNA samples?

• A blue color

• No color change

• A lighter color

• A darker color

What does diphenylamine react with in the DNA molecule?

• Hydrogen

• Nitrogen

• Carbon

• Oxygen

What did the teacher conclude about the presence of DNA in the samples?

• The samples contained RNA

• The samples definitely contained DNA

• Further tests are needed to confirm the presence of DNA

• The samples did not contain DNA

What will the class do next time to confirm the presence of DNA?

• Boil the samples for a longer time

• Perform additional chemical tests

• Use a different chemical

• Run the same test again