2. Allele: One member of a pair of genes occupying a specific spot on a chromosome that controls the same trait.
3. Chromosome: A structure within the cell that bears the genetic material of an organism.
4. Codominance: A condition in which the alleles of a gene pair in a heterozygote are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive. Example: AB Blood Type
5. Dominant Allele: The allele that determines the phenotype of an organism, masking the effect of the recessive allele when present.
14. Incomplete Dominance: A kind of dominance occurring in heterozygotes in which the dominant allele is only partially expressed. This usually results in offspring with an intermediate phenotype because the organism has one dominant allele and one recessive allele.
16. Monohybrid Cross: A crossbreeding experiment that follows the inheritance of a single characteristic across one or more generations. In other words this is a cross of one trait from two parents.
18. Phenotype: The physical appearance of an organism as a result of the interaction of its genotype and the environment.
19. Polygenic Trait: A trait that is controlled by two or more genes at different loci on different chromosomes. Examples: height, skin color, weight.
20. Recessive: An allele whose phenotypic expression is masked by a dominant allele. The recessive trait may be expressed when the recessive genes are in a homozygous condition.
21. Trait: A qualitative characteristic. An attribute of phenotype, not of genotype.