Punnett Squares
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PUNNETT SQUARES
Homozygous
Having a pair of identical alleles
Heterozygous
Having two different alleles for a gene
Phenotype
Organism's traits
Genotype
Organism's genetic makeup
Punnett Squares
- For crosses involving a single trait, used a four-squared Punnett Square
- Use upper-case letters to denote dominant allele
- Use lower-case letters to denote recessive allele
- Place one allele above each column and one allele before each row
- In the boxes, write the combination of the two alleles
Testcross
A cross that allows one to determine the genotype of an individual by crossing it with a homozygous recessive individual and looking at the offspring