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Genes

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.

References

Gene. Taber's Medical Dictionary Online. www.tabers.com/tabersonline/view/Tabers-Dictionary/729952/all/gene. Accessed June 11, 2019.

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.

    • Chromosomes and DNA

      Chromosomes and DNA - illustration

      Humans typically have 23 pairs of chromosomes, or 46 chromosomes in total. Chromosomes are made up of long strands of DNA, which contain all the body's genes.

      Chromosomes and DNA

      illustration

      • Chromosomes and DNA

        Chromosomes and DNA - illustration

        Humans typically have 23 pairs of chromosomes, or 46 chromosomes in total. Chromosomes are made up of long strands of DNA, which contain all the body's genes.

        Chromosomes and DNA

        illustration

      Review Date: 5/13/2019

      Reviewed By: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

      The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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