Genetics Problems—Single Trait Crosses
Trait
Dominant Allele
Short hair (H)
Recessive Allele
Long hair (h)
Name: ____________________________
Directions:
Three different traits in cats are listed in
the chart on the left. For each question,
Coat length
Tabby (T)
Stripeless (t)
Normal (N)
Colorpoint (n)
Tabby (stripes)
Colorpoint (dark
markings on
nose, ears, tail)
1. identify the allele cross
2. complete a Punnett square
3. identify the Phenotype Ratio and
Genotype Ratio for each cross.
1. Word cross: Homozygous Short Hair x Homozygous Long Hair
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
2. Word cross: Heterozygous Short Hair x Heterozygous Short Hair
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
3. Word cross: Homozygous Stripeless x Heterozygous Tabby
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
4. Word cross: Purebred Tabby x Hybrid Tabby
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
5. Word cross: Colorpoint x Colorpoint
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
6. Word cross: Hybrid Normal x Hybrid Normal
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
7. Word cross: Heterozygous Normal x Homozygous Normal
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
8. Word cross: Purebred Stripeless x Hybrid Tabby
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
9. Word cross: Homozygous Stripeless x Purebred Tabby
Allele Cross: _________ x __________
Genotype Ratio:
Phenotype Ratio:
10. Going further: If you had a Tabby cat and wanted to know if this cat was Homozygous or
Heterozygous, what type of cat could you breed your Tabby with to prove its genotype? Explain
your answer (Hint: look at #8 and #9).