A physical characteristic of an organism determined by genes
Different possible types of a trait
Purple flower and white flower are examples of different alleles for flower color.
The genetic makeup of a trait
To visualize the genetic makeup of a trait, letters are used to represent different types of traits.
The letters PP are used to represent the genotype for a purple flower
The physical characteristic that results from a genetic trait
The purple flower
When an organism possesses both alleles for the same trait it is said to be homozygous. We represent homozygous individuals with either two upper case letters or two lower case letters.
When an individual has two different alleles for the same trait, we would use one upper case letter and one lowercase letter to display their genotype.