Download Playing with Punnett Squares

Playing with Punnett Squares
SYNOPSIS
Students practice using Punnett squares while creating a creature with known
alleles for various characteristics.
OBJECTIVE
Students will be able to demonstrate the accurate use of a Punnett square to
determine the genotype and phenotype of a character trait that follows simple
dominance inheritance.
MATERIALS (one / student or group)
• blank paper
• colored pencils
• one set of parental alleles (see attached)
• pencil
VOCABULARY
inheritance: attributes acquired via biological heredity from the parents
Punnett square: a chart that shows all the possible gene combinations for a
cross between parents with known genes
BACKGROUND
Depending on grade level and prior knowledge of students, provide information
about genes, alleles, recessive, dominant, and inheritance. The characteristics
being examined in these fictional creatures are all transmitted through simple
dominance inheritance. This means that there are two alleles at one locus. The
dominant allele will dominate over the recessive allele that is masked or
covered.
PROCEDURES
1. Teach/review content and vocabulary as necessary. Teach students how
to create and use Punnett squares.
2. Explain to students they will draw a creature based on given
characteristics. They will then need to discern at least one possible
genotype each for the female and male parent, then create a Punnett
square using their data. Students will circle their creatures’ genotype
in each of the Punnett squares they create for each characteristic. The
creature should be drawn on one side of the blank paper and the
Punnett squares on the other.
3. Divide the students into groups of three to four students.
4. Distribute the necessary materials to the students, including the sheet
listing the creatures’ genotypes.
a. Explain the worksheet: The creature’s genotype is listed on the left.
The dominant and recessive characteristics are listed on the right.
The students should draw their creature based on its genotype.
b. Students should fill in the male and female parent columns with
possibilities of the genotypes. They will use this information to
create their Punnett squares.
5. As students work in groups, assist them as necessary. Question them
about the drawing of their creature to ensure they are showing the
creature’s correct phenotype based on its genotype. Check their
Punnett squares for accuracy.
CHECK FOR UNDERSTANDING
- Ask the students how they were able to determine at least one possible
genotype for the female and male parents.
- Ask the students the options for parent genotypes if an offspring has a
recessive trait (either Aa or aa for both of the parents)
- Ask the students what the parents’ genotypes are when the offspring are
AA, Aa, aA, and aa (both parents are heterozygous: Aa and Aa)
- Ask the students what happens when both parents are homozygous
dominant (all offspring are AA)
EXTENSION
- Show the students how to create a Punnett square that includes multiple
characteristics (dihybrid crosses).
- Create Punnnett squares crossing the given creatures to find out what the
offspring will look like.
- Students create their own creatures using the dominant and recessive
characteristics given, and then trade them with other students who then
guess the genotype of the creature based on its phenotype.