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Inherited Disorders and Birth Defects

Chromosome disorder



What are the effects in toddlers of a chromosome disorder?


Chromosomes are string-like structures found in the nucleus of our cells. It is estimated that chromosomes contain about 25,000 to 30,000 gene pairs that tell the body how to grow and develop as well as determine such traits like eye and hair color. Each person normally has 46 chromosomes or 23 pairs. We normally inherit one chromosome of each pair from our mother and one from our father.

A child can be born with too many or too few chromosomes, or with one or more chromosomes that are broken so that there is a piece missing (deletion) or added (duplicated) or rearranged. Errors in the number or structure of chromosomes cause a wide variety of birth defects ranging from mild to severe.

The types of problems or abnormalities that would be seen - the phenotype - would depend on what chromosome is involved and what genes were located on the part of the chromosome that was missing or duplicated and how much of the chromosome material was involved.

Chromosome abnormalities usually lead to changes in growth - usually small, the possibility of having major birth defects such as congenital heart defects or a cleft lip and palate, delays in development and mental retardation. Depending on the chromosome involved – what is seen can be very variable.

The most common chromosomal abnormality seen in live born infants is Down syndrome (trisomy 21 – having a whole extra number 21 chromosome).

There is an excellent website - Chromosome Deletion Outreach - listed below that has additional information.

Related Resources:

Chromosome Deletion Outreach

For more information:

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Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University