Genetics and Heredity Quiz

An organism's expressed physical traits, such as hair color or shape, are called its phenotype. Phenotype is determined by such factors as an individual's genotype and expressed genes.

An allele is an alternative version of a gene. Alleles determine distinct traits that are passed from parents to offspring through sexual reproduction.

Heterozygous refers to having two different alleles for a trait. If one allele is dominant and the other recessive, the recessive trait is masked in the phenotype.

In incomplete dominance relationships, one allele for a specific trait is not completely expressed over its paired allele. A third phenotype is observed in which the characteristic is a mixture of the dominant and recessive phenotypes.

The genotype for a plant with white flowers would be (rr). The alleles in this example are homozygous recessive.

In a dihybrid cross, organisms differ in two traits.

In this type of monohybrid cross, the resulting plants will have all green peas. These plants will all be heterozygous for green pea color (Gg). The dominant green color masks the recessive yellow color resulting in a phenotype of all green peas.

The principle of independent assortment states that alleles separate independently of one another at gamete formation. Gametes are formed by the process of meiosis. Allele pairs are then randomly united at fertilization.

In X chromosome linked recessive traits, the phenotype is always expressed in males. Males have only one X sex chromosome. As such, sex-linked traits on this chromosome are always expressed in males.