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Name: Anonymous
Status: Student
Age: 20s
Location: N/A
Country: N/A
Date: 2001


Question:
I recently had to complete genetics problems using the Punnet square. I drew the squares and did all of the calculations properly and obtained the correct answers. Points were taken off my quiz because in my diagram of the Punnet square, I did not circle the individual gametes that were symbolized. My professor claims that the proper way to complete a Punnett square is by circling each individual gamete representation in the diagram.

I have not been able to find any information to support this claim and even in our text, the gametes in the Punnet square examples are not circled. My professor claims that the text examples are not in the proper format. Is this true and where can I find it?



Replies:
Far be it from me to argue with your professor, but if that is true then every genetics book I have ever seen is in the wrong form. I have never seen that. But if that is what your professor wants and if he made that clear then the correct answer is whatever he says it is!

vanhoeck


Aaron,

If this was just a quiz, I would not get too excited over this. In the future, if your prof. feels the text is not accurate, he might choose another with which he agrees.

In the long run, getting the right answer is the goal, but within education the method is often stressed. If your prof. expects demonstration of the method he is teaching, it creates an easier life by complying. naturally, a challenge to his opinion can be mounted, but it is often easier and wiser (especially when you need his letter of recommendation for graduate school) to meet and exceed his expectations.

In my opinion, you made your point. I would just move on and rely on his teaching, less on the text.

Just my 2 cents, less taxes.

Ric Rupnik
Thanks for using NEWTON!


I am not sure what you mean, but if you mean you gave the correct probabilities and drew the Punnett square out correctly and simply failed to circle the gametes It seems rather picky to me, unless, of course you were specifically instructed to do so. Although circling gametes is found in some texts it is not any sort of "rule". Furthermore, some texts are not consistent when they illustrate the Punnett square, sometimes circling and sometimes not eg. Botany by Mauseth. The circle usually indicates the phenotypes of the f2 generation but if you gave that information in your answer I am not sure what more information the circle gives. I checked my extensive library and some very good texts do not circle the gametes...eg. Cell Biology by Robert Dyson...some do. Various Genetics web sites like the one a U. Texas below in their instructions of using the Punnett square do not employ the circling of gametes neither do many others q.v below.

http://www.esb.utexas.edu/dr/UT-TAMU%20material/Class%202%20Sept%204%20Proba bility%20-%20Models/Prob.%20and%20Mendel%20-%20John/sld014.htm

http://tidepool.st.usm.edu/crswr/punnett.html

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy


Hmm, I guess the question is "did the professor tell you ahead of time to circle the gametes (i.e., to make sure you knew where the gametes are located on the square)?" If he did, then I think you are out of luck... That being said, I have worked in the fields of molecular and classical genetics for many years, and have never seen the gametes circled. Nor has my wife, who taught genetics at UCLA for 10 years. A word to the wise, pick your fights wisely.

Paul Mahoney, Ph.D.



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