3033 Lab 2
Genotype and Phenotype
Anna Blight
When this lab is completed, students will be able to:
Explain the definition of alleles, and determine dominant or recessive alleles
Define homozygous, heterozygous, homozygous dominant, and homozygous
Specify dominant or recessive traits for cattle and sheep
Define genotype and phenotype and give examples of each
Prepare and interpret a Punnett square
Demonstrate knowledge of the expected outcome of animal crosses
Organize data to calculate genotypic and phenotypic ratios
Sequence data to illustrate multiple traits on a Punnett square
Materials: black and red checkers, for black or red Angus or Holsteins, mixed in a bag
black and white chips or buttons for black or white sheep, mixed in a bag
Punnett square sheets with 9 cells
art paper and markers
Procedure: have students count off by 2’s. Each person in the group of 2 then chooses 2
chips from the cattle bag or each takes 2 from the sheep bags.
Tell the students that some traits are dominant and some are recessive. If they chose a
black chip from the cattle bag, they have a dominant allele, if they pick red it is a
recessive allele. For sheep, white is the dominant allele and black the recessive allele.
Ask them to record the genotype of their animals. The 2 students will cross their animals
to see what genotype and phenotype the offspring will be. Have them fill in the Punnett
square and tell what the genotypes are. Then tell them to draw the phenotype of the four
offspring.
Next, tell the student to cross two of their offspring to get the F2 generation and fill in
the Punnett square.