Information for Parents & Families

Recessive Inheritance

The advice below is produced by the National Centre for Medical Genetics (NCMG) and is for educational purposes only. If you need more advice about recessive inheritance, please contact:

The National Centre for Medical Genetics

CHI at Crumlin

Children's Health Ireland at Crumlin

D12 N512


Telephone: 01 409 6100 Fax: 01 455 8873

What is a Genetic Mutation?

Genes are the unique set of instructions in every cell which make each of us individual. There are many thousands of genes, each carrying a different instruction. If a gene is altered, it can cause a genetic condition or disease. This gene alteration is known as a mutation.

What does Recessive Inheritance Mean?

Some conditions are inherited in a way that is called recessive. Individuals who have two altered copies of a gene are affected with the condition. Individuals who have only one altered copy of gene are usually completely healthy.

They are known as carriers because they carry one altered copy of a gene. Their normal copy of the gene keeps them healthy and compensates for the altered copy.

Having Children

If both healthy parents carry the same altered recessive gene, then there are four possible outcomes for each pregnancy they have, regardless of the sex of the child (see Diagram 1):

  • A one in four (25%) chance of inheriting the altered gene from both parents and being affected
  • A one in two (50%) chance of inheriting the altered gene from one parent and therefore being a healthy carrier
  • A one in four (25%) chance of inheriting the normal gene from both parents and being neither a carrier nor affected

If only one parent is a carrier of the altered gene, then each of their children has a one in two (50%) chance of being a healthy carrier, but will not be affected (see Diagram 2). If one parents is affected and the other is a carrier, then each of their children will have a 50% chance of being affected and 50% chance of being a carrier (see Diagram 3). If one parent is affected with the condition, then each child will be a carrier but not affected, once the other parent is not a carrier (see Diagram 4)

Couples who are closely related to each other (eg: first cousins) are more likely to share a copy of the same altered gene, thereby increasing the likelihood of having a child with a recessively inherited condition.

RD COllage


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This educational content has been developed independently of the UCD School of Medicine and is being hosted here to assist the clinical group in disseminating useful public health information.

Presenter: Dr Kirsten FitzGerald

Commissioning Investigator : Dr Sally Ann Lynch

Project Manager: Dr Jillian Casey

Video Production : UCD Media Services

Copyright: Dr Kirsten FitzGerald


Social Welfare Supports

Ms Alison Wilson Wilson (Genetic counsellor, MPS All Ireland Advocacy Support Group) has kindly put together the attached document which summarises the key Social Welfare Supports available to those living with long-term illness or disability.

Information Guide: Social welfare payments which are available to people living with a long-term illness or disability.

Please note that this document is provided in good faith, is intended for information purposes and is correct at the time of publishing (September 2014).  The content may be subject to ongoing change.   For professional advice and support please contact your local Citizens Information Office or visit

Cleft Lip and/or Cleft Palate

The Genetics Teams at National Centre for Medical Genetics and CHI at Temple Street have produced a short information guide on cleft lip/palate for parents and families.

Guide to Cleft Lip and Cleft Palate for Patients and Families.

This document is reproduced here with the permission of the authors. 

Further information can be obtained from the Cleft Lip & Palate Association of Ireland at