XYY Karyotype Health Channel

Definition

Genetics is the study of heredity, the process in which a parent passes certain genes onto their children. A person's appearance -- height, hair color, skin color, and eye color -- are determined by genes. Other characteristics affected by heredity:

• Likelihood of getting certain diseases
• Mental abilities
• Natural talents

An abnormal trait (anomaly) passed down through families (inherited) may:

• Have no effect on your health or well being -- for example, it may just involve a white patch of hair or an extended earlobe
• Be of minor consequence -- for example, color blindness
• Have a dramatic effect on your quality or length of life

For most genetic disorders, genetic counseling is advised. Many people may also want to seek prenatal diagnosis.

The terms anomaly, abnormality, disorder, defect, disease, and syndrome are not used consistently, and do not have precise definitions.

Alternative Names

Homozygous; Inheritance; Heterozygous; Inheritance patterns; Heredity and disease; Heritable; Genetic markers

Information

Human beings have cells with 46 chromosomes -- 2 sex chromosomes and 22 pairs of nonsex (autosomal) chromosomes. Males are "46, XY" and females are "46, XX." The chromosomes are made up of strands of genetic information called DNA.

Genes are sections of DNA. The location of the gene is called the locus. Most genes carry information that is necessary to make a protein.

The pairs of autosomal chromosomes (one from the mother and one from the father) carry basically the same information. That is, each has the same genes. However, there may be slight variations of these genes. These slight differences occur in less than 1% of the DNA sequence and produce variants of a particular gene called alleles.