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The information contained on this page is provided as general health information and is not intended to substitute as medical advice and direction from your physician or health care provider. Please direct any questions related to your health care provider. In an emergency, call 9-1-1 or go to the nearest emergency center.


Genes

Definition

A gene is a short piece of DNA. Genes tell the body how to build specific proteins. There are about 20,000 genes in each cell of the human body. Together, they make up the blueprint for the human body and how it works.

A person's genetic makeup is called a genotype.

Information

Genes are made of DNA. Strands of DNA make up part of your chromosomes. Chromosomes have matching pairs of 1 copy of a specific gene. The gene occurs in the same position on each chromosome.

Genetic traits, such as eye color, are dominant or recessive:

  • Dominant traits are controlled by 1 gene in the pair of chromosomes.
  • Recessive traits need both genes in the gene pair to work together.

Many personal characteristics, such as height, are determined by more than 1 gene. However, some diseases, such as sickle cell anemia, can be caused by a change in a single gene.

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Chromosomes and DNA

References

Gene. Taber's Medical Dictionary Online. www.tabers.com/tabersonline/view/Tabers-Dictionary/729952/all/gene. Accessed June 11, 2017.

Nussbaum RL, McInnes RR, Willard HF. The human genome: gene structure and function. In: Nussbaum RL, McInnes RR, Willard HF, eds. Thompson & Thompson Genetics in Medicine. 8th ed. Philadelphia, PA: Elsevier; 2016:chap 3.