Genetic Rules to Follow
Always circle or underline key words within your paragraph/word
problems. This will help you to create your genotypes, phenotypes,
males vs females etc. for your Punnett squares.
Homozygous: same capitalization (Homo means “same”)
Heterozygous: different capitalization (Hetero means “different”)
Recessive: lowercase letter
Dominant: Uppercase letter
Purebred: must have the same capitalization
Hybrid: are heterozygous
Genotype: The trait represented by the letter combination
Phenotype: The description of the trait/the physical characteristic you see
Sex Linked Traits
Males: XY and carry the trait ONLY on the X chromosome
Females: XX and can carry the trait on both X chromosomes
Multiple Alleles (Blood Type)
See the Amoeba Sisters worksheet
Dihybrid Cross
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16 squares each worth 6.25%
Each parent needs to be “FOILED”
FOIL (First, Outside, Inside, Last)
Incomplete Dominance
1. There are NO lowercase letters
2. NEITHER trait is dominant or recessive
3. A mixed color or blended color is made (like when you mix red paint and white paint makes
pink)
4. The mixed color they make is heterozygous
Codominance
1. There are NO lowercase letters
2. This time both traits express themselves in different locations
3. Both colors are represented by the dominant homozygous letters (Purebred RR-RED and WWWHITE )
4. And when both colors show they will be written as a hybrid (RW hybrid- heterozygous)