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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.


Genes are made of DNA. Strands of DNA make up part of your chromosomes. Chromosomes have matching strands of DNA that make specific genes. Except for the sex chromosomes (X and Y), chromosomes are paired so there are 2 genes, 1 on each chromosome. 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.


Chromosomes and DNA
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.


Biesecker LG. Clinical genomics-genome structure and variation. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 36.

Taber's Cyclopedic Medical Dictionary. 24th ed. Gene. Philadelphia, PA: F.A. Davis Company; 2021. Accessed June 13, 2023.

Last reviewed April 27, 2023 by Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team..

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Clinical Trials: Genes

UF Health research scientists make medicine better every day. They discover new ways to help people by running clinical trials. When you join a clinical trial, you can get advanced medical care. Sometimes years before it's available everywhere. You can also help make medicine better for everyone else. If you'd like to learn more about clinical trials, visit our clinical trials page. Or click one of the links below:


Development of a central repository for PD-related genomic data for future research.

Irene A Malaty
Accepting Candidates
18 Years - N/A
View all genes studies

News and Patient Stories: Genes

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