How Are Characteristics Inherited in Humans?

How Are Characteristics Inherited in Humans?

Human characteristics are inherited through DNA that the child receives from his mother and father. Traits may be determined by a single gene on the DNA or multiple genes. Each person has two sets of each gene, one from each parent.

One simple example is whether a person has attached ear lobes or hanging earlobes. The gene for hanging earlobes is dominant. If a person has two copies of the recessive earlobe gene, he has attached earlobes. If one or both of the genes are dominant, he has free-hanging earlobes. Many other characteristics, including skin and eye color, are determined by multiple genes.

Gender is determined by a single set of chromosomes. Females have two X chromosomes, while males have one X and one Y chromosome. Genes for some characteristics are located on these sex chromosomes. For example, red-green color blindness is determined by a gene on the X chromosome. If a male receives a normal copy of the gene, he sees color normally, but if he receives the gene for red-green colorblindness, he has the condition. For a woman to be red-green colorblind, she would have to receive two copies of the gene for this colorblindness, one from each of her parents.