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Cornsnake Morph Guide ®

Genetics Tutorial

Charles Pritzel

Step 10: Practice

Nobody has genetics mastered in the first run through. When you learned something new in school, you had to practice. Likewise, it takes some practice to become comfortable with approaching these problems. Following are some examples that can be used for practice. An answer key is provided on the next page. More examples/answers are available at http://cornguide.com/quiz.php.

Beginner:

(Hint: use FOIL)
1- Cross aa X AA.
2- Cross Aa X aa.
3- Cross AA X Aa.
4- Cross Aa X Aa.

Intermediate:

(Hint: use FOIL on each trait individually, then combine them using a grid.)
5- Cross aaBB X AAbb.
6- Cross Aabb X aaBb.
7- Cross aaBb X AaBb.
8- Cross AaBb X AaBb

Advanced:

(Hint: use FOIL on each trait, then add in each new trait's results by using a grid.)
9- Cross AABBcc X aabbCC.
10- Cross Aabbcc X aaBbcc.
11- Cross AaBbCC X aabbCc.
12- Cross AaBbCc X AaBbCc.

With practice, you will find that there are only six basic crosses, and FOIL isn't needed any more once these have been memorized.

Expert:

(Use the shortcut in Step 9.)
13- When crossing AaBbCcDd X AabbccDd, what are the odds of getting the genotype aa bb cc dd?
14- When crossing aabbccdd X AaBbCcDd, what are the odds of getting aa bb cc dd?
15- When crossing AaBbCcDd X AaBbCcDd, what are the odds of getting aa bb cc dd?
16a- When crossing AaBbCcDd X AaBbCcDd, what are the odds of getting anything expressing the recessive a and b traits?

16b- What are the odds of getting anything expressing recessive traits b and c, but not expressing recessive traits a and d?

More practice problems/answers are available in the genetics quiz.

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