Punnett Square Problems


B=blonde hair                    b=brown hair              E=blue eyes       

T=tall                                  t=short                       e=brown eyes

R=round                             r=wrinkled

Use the key above and answer the following questions. 

1.  In the genotype Bb, what is the dominant letter and corresponding trait and what is the recessive letter and

     corresponding trait? _____________________________________ 

  2.  When crossing a heterozygous trait with a homozygous trait, what is the resulting genotype ratio? 



  3A. Using the Punnett Square below, correctly cross a heterozygous blue eyed person with a

    homozygous brown eyed  person.          







3B. In the corresponding F2 generation, what will the phenotype ratio be? _________________________

       What are those specific phenotypes? (i.e. tall, short etc)_________________________





4.  A person has blonde hair and is heterozygous dominant for this trait. 

Give me the genotype for this person.  ________________________                                 



5.  What is the difference between a genotype and a phenotype? 


  6.  What did Mendel use in his first experiment to test his hypothesis about genes?  (Be specific)



7.  A person is very short.  They are homozygous recessive for this trait.  Give me the genotype for this person. 



8.  Joe and Liz are expecting their first child.  Liz has brown eyes and Joe has green.  Joe would like a child with green

     eyes (G) and Liz would like a child with brown eyes (g). Given that Liz is homozygous for her brown eyes, and Joe is

     heterozygous for his green, what are the chances their children will get the eyes Liz and Joe want?


9. Draw a Punnett square (16 boxes) for dihybrid crosses and cross straight blonde hair (SB), curly blonde hair (sB), 

    straight red hair (Sb) and curly red hair (sb).  What is the phenotype ratio?