Download Key Terms

Punnett Square Quiz Study Guide
Key Terms

Trait – a characteristic of an organism

Allele – different forms a gene may have for a trait; the letter used to represent it

Genotype – the genetic makeup of an organism; alleles in a gene pair

Phenotype – a physical trait that shows as a result of an organism’s particular
genotype; what the trait looks like

Dominant – form of a trait that overshadows another form of the same trait

Recessive – form of a trait that can be overshadowed by a more dominant trait

Homozygous – an organism that has two identical alleles for a trait; ie. TT, tt

Heterozygous – an organism that has two different alleles for a trait; ie. Tt

Purebred – an organism that has two identical alleles for a trait; ie. TT, tt

Hybrid – an organism that has two different alleles for a trait; ie. Tt

P1 – parent generation; first two organisms crossed

F1 – first offspring generation; first offspring created

F2 – second offspring generation; second offspring created from breeding F1s
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1/4 squares = 25%
2/4 squares = 50%
3/4 squares = 75%
4/4 squares = 100%
***You need to know how to complete Punnett squares, analyze them, and
determine genotypic and phenotypic ratios. There are practice problems
below and on the back of this sheet.***
rr x Rr
MM x Mm
QQ x qq
Genotypic ratio:
Genotypic ratio:
Genotypic ratio:
Phenotypic ratio:
Phenotypic ratio:
Phenotypic ratio:
Dominant: Purple
Recessive: White
Parents: Pp x pp
What are the phenotypes of the offspring?
What % of the offspring will have purple flowers?
What is the genotypic ratio?
What is the phenotypic ratio?
How many different genotypes do the offspring have?
Dominant: Curly hair
Recessive: Straight hair
Parents: Homozygous curly x homozygous straight
What are the phenotypes of the offspring?
What % of the offspring will have curly hair?
What is the genotypic ratio?
What is the phenotypic ratio?
How many different genotypes do the offspring have?
Dominant: Brown eyes
Recessive: Blue eyes
Parents: Heterozygous brown x heterozygous brown
What are the phenotypes of the offspring?
What % of the offspring will have brown eyes?
What is the genotypic ratio?
What is the phenotypic ratio?
How many different genotypes do the offspring have?
In pea plants, green seeds are dominant over yellow seeds. If a hybrid plant is crossed
with another hybrid plant, what is the probability (%) that they will have children with
green seeds? Yellow seeds? Draw a Punnett square to support your answer.