SIGN IN YOUR ACCOUNT TO HAVE ACCESS TO DIFFERENT FEATURES

FORGOT YOUR PASSWORD?

FORGOT YOUR DETAILS?

AAH, WAIT, I REMEMBER NOW!
24/7 HELPLINE (903) 212-7500
  • PATIENT PORTAL LOGIN

PhyNet Health PhyNet Health

  • Home
  • Find a Clinic
    • Hughes Springs, TX
    • Longview, TX
    • Jefferson, TX
    • Kilgore, TX
    • Lindale, TX
    • Linden, TX
    • Gladewater, TX
    • Lone Star, TX
    • Tatum, TX
    • Marshall, TX
  • Health Services
    • Primary Care Services
    • Physical Therapy / Rehab
    • Allergy Testing & Treatment
    • Chronic Care Management
    • Remote Monitoring Program
    • Virtual Visit
  • Resources
    • MedlinePlus Wiki
      • Health Topics
    • Home Health Coordination
    • Transitions of Care
    • Insurance Help
  • About Phynet
    • About Phynet
    • PhyNet News
    • Better Together Stories
    • Careers
  • Billing

Health Topics

Skip navigation

An official website of the United States government

Here’s how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( Lock Locked padlock icon ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

National Institutes of Health National Library of Medicine
MedlinePlus Trusted Health Information for You
  • Health Topics
  • Drugs & Supplements
  • Genetics
  • Medical Tests
  • Medical Encyclopedia
  • About MedlinePlus
  • About MedlinePlus
  • What's New
  • Site Map
  • Customer Support
  • Health Topics
  • Drugs & Supplements
  • Genetics
  • Medical Tests
  • Medical Encyclopedia
Español
You Are Here:
Home →
Genetics →
Help Me Understand Genetics →
Variants and Health →
What is a gene variant and how do variants occur?
URL of this page: https://medlineplus.gov/genetics/understanding/mutationsanddisorders/genemutation/

What is a gene variant and how do variants occur?

A gene variant is a permanent change in the DNA sequence that makes up a gene. This type of genetic change used to be known as a gene mutation, but because changes in DNA do not always cause disease, it is thought that gene variant is a more accurate term. Variants can affect one or more DNA building blocks (nucleotides) in a gene.

Gene variants can be inherited from a parent or occur during a person’s lifetime:

  • Inherited (or hereditary) variants are passed from parent to child and are present throughout a person’s life in virtually every cell in the body. These variants are also called germline variants because they are present in the parent’s egg or sperm cells, which are also called germ cells. When an egg and a sperm cell unite, the resulting fertilized egg cell contains DNA from both parents. Any variants that are present in that DNA will be present in the cells of the child that grows from the fertilized egg.
  • Non-inherited variants occur at some time during a person’s life and are present only in certain cells, not in every cell in the body. Because non-inherited variants typically occur in somatic cells (cells other than sperm and egg cells), they are often referred to as somatic variants. These variants cannot be passed to the next generation. Non-inherited variants can be caused by environmental factors such as ultraviolet radiation from the sun or can occur if an error is made as DNA copies itself during cell division.  

Some genetic changes are described as new (de novo) variants; these variants are recognized in a child but not in either parent. In some cases, the variant occurs in a parent’s egg or sperm cell but is not present in any of their other cells. In other cases, the variant occurs in the fertilized egg shortly after the egg and sperm cells unite. (It is often impossible to tell exactly when a de novo variant happened.) As the fertilized egg divides, each resulting cell in the growing embryo will have the variant. De novo variants are one explanation for genetic disorders in which an affected child has a variant in every cell in the body, but the parents do not, and there is no family history of the disorder.

Variants acquired during development can lead to a situation called mosaicism, in which a set of cells in the body has a different genetic makeup than others. In mosaicism, the genetic change is not present in a parent’s egg or sperm cells, or in the fertilized egg, but happens later, anytime from embryonic development through adulthood. As cells grow and divide, cells that arise from the cell with the altered gene will have the variant, while other cells will not. When a proportion of somatic cells have a gene variant and others do not, it is called somatic mosaicism. Depending on the variant and how many cells are affected, somatic mosaicism may or may not cause health problems. When a proportion of egg or sperm cells have a variant and others do not, it is called germline mosaicism. In this situation, an unaffected parent can pass a genetic condition to their child.

Most variants do not lead to development of disease, and those that do are uncommon in the general population. Some variants occur often enough in the population to be considered common genetic variation. Several such variants are responsible for differences between people such as eye color, hair color, and blood type. Although many of these common variations in the DNA have no negative effects on a person’s health, some may influence the risk of developing certain disorders.

For more information about variants:

The National Human Genome Research Institute (NHGRI) provides a fact sheet discussing human genomic variationFrom the National Institutes of Health.

The Centre for Genetics Education provides a fact sheet discussing variations in the genetic code.

KidsHealth from Nemours offers an introduction to genes, genetics, and genetic changes.

Additional information about genetic alterations is available from the University of Utah: "What is Mutation?"

Topics in the Variants and Health chapter

  • What is a gene variant and how do variants occur?
  • How can gene variants affect health and development?
  • Do all gene variants affect health and development?
  • What kinds of gene variants are possible?
  • Can a change in the number of genes affect health and development?
  • Can changes in the number of chromosomes affect health and development?
  • Can changes in the structure of chromosomes affect health and development?
  • Can changes in noncoding DNA affect health and development?
  • Can changes in mitochondrial DNA affect health and development?
  • What are complex or multifactorial disorders?
  • What does it mean to have a genetic predisposition to a disease?
  • How are gene variants involved in evolution?
  • What information can statistics provide about a genetic condition?
  • How are genetic conditions and genes named?

Other chapters in Help Me Understand Genetics

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.

  • About MedlinePlus
  • What's New
  • Site Map
  • Customer Support
  • Subscribe to RSSRSS
  • Connect with NLM
  • NLM Web Policies
  • Copyright
  • Accessibility
  • Guidelines for Links
  • Viewers & Players
  • HHS Vulnerability Disclosure
  • MedlinePlus Connect for EHRs
  • For Developers
National Library of Medicine 8600 Rockville Pike, Bethesda, MD 20894 U.S. Department of Health and Human Services National Institutes of Health
Last updated March 25, 2021
Return to top

Patients

  • Find a Clinic
  • Health Services
  • Complex Case Management
  • MA / Medicare Assistance

Quick Links

  • Billing Information
  • Careers
  • About Phynet
  • PhyNet News

Network Links

  • PrimeCareHomeHealth.com
  • PrimeCareNet.com
  • PrimeCareManagers.com
  • Core-Rehab.com

Home Office

4002 Technology Center Longview TX 75605
Phone: (903) 247-0484
Fax: (903) 247-0485
[email protected]
  • PrimeCareHomeHealth.com
  • PrimeCareNet.com
  • PrimeCareManagers.com
  • Core-Rehab.com
  • GET SOCIAL

© 2021 PhyNet Health • All rights reserved
YOUR LIFE. YOUR CHOICE.

TOP