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section of DNA that codes for a protein and determines a trait


specific characteristic that varies from one individual to another


alternative forms of a gene


trait that will show up in an organism's phenotype if gene is present


trait that will only appear in the phenotype if organism inherits two of them; covered up by the dominant gene


separation of alleles during meiosis or gamete formation


sex cell; sperm or egg


offspring of a cross between parents with different traits; heterozygous


inherited two identical alleles for a trait; homozygous or purebred


likelihood an event will occur


physical characteristics of an organism, observable or measurable

Punnett square

diagram that shows the possible results of a genetic cross; parents' gametes on top and left, offsprings' genotypes inside


genetic makeup of an organism


has two identical alleles for a particular trait; true-breeding or purebred, ex. PP or pp


has two different alleles for a particular trait; hybrid, ex. Pp

independent assortment

principle that genes do not influence each other's inheritance because they are separated independently during meiosis

multiple alleles

three or more alleles exist for a particular trait

incomplete dominance

creates a blended phenotype; one allele is not completely dominant over the other

polygenic trait

trait controlled by two or more genes; shows a wide variety of phenotypes


both genes contribute to the phenotype of the organism, ex. spotted or striped


error in meiosis in which homologous chromosomes don't separate; gametes end up with wrong number of chromosomes

sex-linked trait

trait related to a gene that is found on the X or Y chromosomes

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