Wentworth-Douglass Hospital
(603) 742-5252
Decrease (-) Restore Default Increase (+) font size
Physicians
Pay Your Bill Online
Pricing Estimates
Financial Assistance
Health Library
Health Insurance Marketplace Assistance
Interpreter and Communication Services
Surgery Preparation
Medical Records
Accountable Care Organization
Advance Directives
Clinical Research & Trials
Food and Nutrition Services
Back to Health Library   Print This Page Print    Email to a Friend Email

Genetics
Genetics


Definition:

Sex-linked diseases are inherited through one of the "sex chromosomes" -- the X or Y chromosomes. Autosomally inherited diseases are inherited through the non-sex chromosomes (autosomes), pairs 1 through 22.

Dominant inheritance occurs when an abnormal gene from one parent is able to cause disease even though the matching gene from the other parent is normal. The abnormal gene dominates.

Recessive inheritance occurs when both matching genes must be abnormal to produce disease. If only one gene in the pair is abnormal, the disease does not show up or is mild. Someone who has one abnormal gene (but no symptoms) is called a carrier. A carrier can pass this abnormal gene to his or her children.

The term "sex-linked recessive" usually refers to X-linked recessive.

See also:



Alternative Names:

Inheritance - sex-linked recessive; Genetics - sex-linked recessive; X-linked recessive



Information:

X-linked diseases usually occur in males. Males have only one X chromosome. A single recessive gene on that X chromosome will cause the disease.

The Y chromosome is the other half of the XY gene pair in the male. However, the Y chromosome doesn't contain most of the genes of the X chromosome. It therefore doesn't protect the male. This is seen in diseases such as hemophilia and Duchenne muscular dystrophy .

TYPICAL SCENARIOS

For a given birth, if the mother is a carrier (only one abnormal X chromosome) and the father is normal:

  • 25% chance of a normal boy
  • 25% chance of a boy with disease
  • 25% chance of a normal girl
  • 25% chance of a carrier girl without disease
If the father has the disease and the mother is normal:
  • 100% chance of a normal boy
  • 100% chance of a carrier girl without disease

X-LINKED RECESSIVE DISORDERS IN FEMALES

Females can get an X-linked recessive disorder, but this is very rare. An abnormal gene on the X chromosome from each parent would be required, since a female has two X chromosomes. This could occur in the two scenarios below.

For a given birth, if the mother is a carrier and the father has the disease:

  • 25% chance of a healthy boy
  • 25% chance of a boy with the disease
  • 25% chance of a carrier girl
  • 25% chance of a girl with the disease

If the mother has the disease and the father has the disease:

  • 100% chance of the child having the disease, whether boy or girl.

The odds of either of these two scenarios are so low that X-linked recessive diseases are sometimes referred to as “male only” diseases. However, this is not technically correct.

Female carriers can have a normal X chromosome that is abnormally inactivated. This is called "skewed X-inactivation." These females may have symptoms similar to those of males.




Review Date: 5/15/2008
Reviewed By: Chad Haldeman-Englert, MD, Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
adam.com


Find What You Need

Events
Careers
Foundation
About Us
Contact
Directions
News
Social Media Agreement
Joint Notice
Web Privacy Policy
WDH Staff Portal

Centers & Services

Cancer Center
Cardiovascular Care
Joint Replacement
Women & Children's
Physician Offices
Other Services

Conditions & Treatments

Health Library

Support Services

Support Groups
Care-Van
Dental Center
Social Work
Food & Nutrition
Integrative Wellness
Spiritual Care
Concerns & Grievances
Homecare and Hospice

For Patients

Pay Your Bill Online
Pricing Estimates
Financial Assistance
Interpreter Services
Surgery Preparation
Medical Record Request
Advance Directives
Clinical Research & Trials

For Healthcare Professionals

Work and Life
Financial Well-Being
Career and Growth

The Wentworth-Douglass Health System includes:

 

Address

Wentworth-Douglass Hospital
789 Central Avenue, Dover, NH 03820
Phone: (603) 742-5252
Toll free: 1 (877) 201-7100