Combinations and Possbilities

Teaching and teaching At-Risk teens

Genetics

“Hey bright eyes…come here often?”
(Melvin always was a sucker for a big-eyed vestigial dame!)

I created the cartoon above, years ago, while in my junior year– Genetics class– at Drury University. Hey, before you roll your eyes…I got 2 bonus points for doing that from an instructor that said he didn’t believe in bonus points. Anyway, I love Genetics. I wrote the curriculum for a semester class that hits the basics for Mendelian Genetics, and I thought I would share one of the lessons that has been successful with my At-Risk students.

Student prep for this lesson: They must have a working genetic vocabulary of: genotype, phenotype, dominant, recessive traits. They must also understand how to create a Punnett square with multiple traits.

Combinations and Possibilities

Directions: First: Write out the possible combination of traits for each of the following genotypes. Second: Then create a Punnett square for couple 1 and 2. Next create a Punnett square for couple 3 and 4. Identify the phenotypical combinations possible and using fractions the phenotypical possibilities for each couples offspring.

1.Man—BbTTCc                2. Woman–BbTtCC

3. Man–bbTTcc                4. Woman–BbttCC

  5. Man—BbTtCc                6. Woman–BBTTCC

Keys:
First Possible combinations– First 1-6

1. BTC–BTc–bTC–bTc

2.  BTC–BtC–bTC—-btC
3.  bTc

4.  BtC–btC
5.  BTC–BtC–BTc–Btc 6. BTC

 

Punnett Square Keys:

#1 and #2 Cross Phenotypical possibilities and fractions for their offspring:

Brown eyes/Tall/Curly hair =  12/16  or   3/4

Blue eyes/Tall/Curly = 4/16  or   1/4

 

#3 and #4 Cross Phenotypical possibilities and fractions for their offspring:

Brown eyes/Tall/Curly = 1/2

Blue eyes/Tall/Curly = 1/2