Punnett Square Representation
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
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?
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!
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.
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.
Peter Faletra Ph.D.
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
Paul Mahoney, Ph.D.
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Update: June 2012