Assignment: Which Has More DNA?

Question: Would a kiwifruit and strawberry that are approximately the same size also have approximately the same amount of DNA?

Background: You have learned that DNA is carried on chromosomes.  All mammals are diploid; however, not all plants are diploid. The common strawberry is octoploid (8n) and the cultivated kiwi is hexaploid (6n). Research the total number of chromosomes in the cells of each of these fruits and think about how this might correspond to the amount of DNA in these fruits’ cell nuclei.

Hypothesis: Hypothesize whether you would be able to detect a difference in DNA quantity from similarly sized strawberries and kiwis. Which fruit do you think would yield more DNA?

Test your hypothesis. Perform the DNA extraction experiment.

Record your observations: Because you are not quantitatively measuring DNA volume, you can record for each trial whether the two fruits produced the same or different amounts of DNA as observed by eye. If one or the other fruit produced noticeably more DNA, record this as well. Determine whether your observations are consistent with several pieces of each fruit.

Analyze your data: Did you notice an obvious difference in the amount of DNA produced by each fruit? Were your results reproducible?

Draw a conclusion: Given what you know about the number of chromosomes in each fruit, can you conclude that chromosome number necessarily correlates to DNA amount? Can you identify any drawbacks to this procedure? If you had access to a laboratory, how could you standardize your comparison and make it more quantitative?

To complete this assessment, address all of the points above in a lab write up. Be sure to include images of your experiment in progress. See the examples contained here.

Basic Requirements (the assignment will not be accepted or assessed unless the follow criteria have been met):

  • Assignment has been proofread and does not contain any major spelling or grammatical errors
  • Assignment includes appropriate references.
  • Assignment addresses the required points noted above (hypothesis, observations/data, analysis of data, conclusion).

Rubric

Which Has More DNA?
Outcome: Relate DNA structure to the process of DNA replication
Criteria Ratings Pts
Hypothesis addresses how the DNA stores genetic information and the role of complementary base pairing in DNA storage/replication. Hypothesis is testable and clearly addresses storage and replication of genetic information.
5.0 pts		 Hypothesis is testable and addresses genetic information storage and replication with some explanation required.
4.0 pts		 Hypothesis is not testable or does not address storage of genetic information and replication of DNA bases.
0.0 pts		 5 pts
Conclusion sections addresses how DNA is used to store genetic information. Conclusion addresses storage of genetic information in detail and references experimental findings directly and in detail.
5.0 pts		 Conclusion addresses storage of genetic information at high level and mentions experimental findings.
4.0 pts		 Conclusion does not address or incorrectly addresses storage of genetic information.
0.0 pts		 5 pts
Total points: 10