Genetics Practice Problems - Simple Worksheet

1.  For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho)

AA _____ Ee ____ Ii _____ Mm _____
Bb _____ ff ____ Jj _____ nn _____
Cc _____ Gg ____ kk _____ oo _____
DD _____ HH ____ LL _____ Pp _____

2.  For each of the genotypes below determine what phenotypes would be possible. 

Purple flowers are dominant to white flowers.

PP __________________

Pp __________________

pp __________________

Round seeds are dominant to wrinkled seeds.

RR __________________

Rr __________________

rr __________________

Brown eyes are dominant to blue eyes

BB ________________

Bb ________________

bb ________________

Bobtails in cats are recessive.

TT _________________

Tt _________________

tt __________________

3.  For each phenotype below, list the genotypes (remember to use the letter of the dominant trait)

Straight hair is dominant to curly.

____ straight

____ straight

____ curly

Pointed heads are dominant to round heads.

_____ pointed

_____ pointed

_____ round

4.  Set up the Punnet squares for each of the crosses listed below. Round seeds are dominant to wrinkled seeds.

Rr x rr
   
   
What percentage of the offspring will be round? _______________
RR x rr
   
   
What percentage of the offspring will be round? _______________
RR x Rr
   
   
What percentage of the offspring will be round? _______________
Rr x Rr
   
   
What percentage of the offspring will be round? _______________

Practice with Crosses.  Show all work!

5.  A TT (tall) plant is crossed with a tt (short plant).  

What percentage of the offspring will be tall?  ___________

6.  A Tt plant is crossed with a Tt plant. 

What percentage of the offspring will be short?  ______

7.  A heterozygous round seeded plant (Rr) is crossed with a homozygous round seeded plant (RR). 

What percentage of the offspring will be homozygous (RR)?  __________

8.  A homozygous round seeded plant is crossed with a homozygous wrinkled seeded plant.

What are the genotypes of the parents?  __________   x  __________

What percentage of the offspring will also be homozygous?  ___________

9.  In pea plants purple flowers are dominant to white flowers.

If two white flowered plants are cross, what percentage of their offspring will be white flowered?  ______________

10.  A white flowered plantis crossed with a plant that is heterozygous for the trait. 

What percentage of the offspring will have purple flowers?___________

11.  Two plants, both heterozygous for the gene that controls flower color are crossed. 

What percentage of their offspring will have purple flowers?  ____________

What percentage will have white flowers?  ___________

12.  In guinea pigs, the allele for short hair is dominant. 

What genotype would a heterozygous short haired guinea pig have?  _______

What genotype would a purebreeding short haired guinea pig have?  _______

What genotype would a long haired guinea pig have? ________

13.  Show the cross for a pure breeding short haired guinea pig and a long haired guinea pig.

What percentage of the offspring will have short hair?  __________

14. Show the cross for two heterozygous guinea pigs.

What percentage of the offspring will have short hair?  ________

What percentage of the offspring will have long hair?  _______

15. Two short haired guinea pigs are mated several times. Out of 100 offspring, 25 of them have long hair. What are the probable genotypes of the parents? 

________   x  ___________            Show the cross to prove it!

 SHOW ALL WORK!