Molecular Rulers

Telomere Study

The Telomere Research Project, led by Drs. David Ledbetter and Christa Lese Martin, is recruiting individuals/families with a previously identified telomere abnormality (that was not discovered on standard chromosome analysis) for fine mapping studies to establish genotype/phenotype correlations. Two categories of telomere rearrangements are of interest: 1) those that are causative of an individual's phenotype and 2) those that were identified in an affected family member, but subsequently found to be carried by an unaffected family member (benign variants). If you would like further information, please contact our project coordinator at (404) 727-7098 or

Marker Chromosome Study

The research laboratory of Dr. David Ledbetter is interested in identifying and characterizing marker chromosomes that remain unidentified after arrayCGH and alpha-satellite FISH studies. We are collecting postnatal or prenatal samples with a marker chromosome that meet the above criteria. Please contact our project coordinator at (404) 727-7098 or for further information regarding inclusion criteria and study details. 

Why are these studies being done?

The purpose of these studies is to determine how often otherwise unexplained developmental disabilities, birth defects and/or pregnancy losses are due to subtle (or very small) chromosome abnormalities. Individuals with a developmental disability may have learning difficulties, mental retardation, behavioral problems (such as autism) or other characteristics. Individuals with birth defects may have a heart defect, cleft lip, cleft palate, spina bifida (hole in the spine) as well as other defects.

If a person has a whole chromosome or part of a chromosome missing or extra, there may be developmental disabilities, birth defects, and/or pregnancy loss. People with all or part of a chromosome missing or extra are said to have UNBALANCED chromosome abnormalities. Some healthy people have a rearrangement of their chromosomes called a BALANCED translocation. If a person has a balanced translocation he/she may have a higher than average risk of having pregnancy losses or a child with developmental disabilities or birth defects because their offspring can inherit UNBALANCED chromosome abnormalities. Sometimes babies are born with balanced or unbalanced chromosome abnormalities even though their parents do not have a chromosome abnormality; these are called de novo (or new) abnormalities.

In this study we are looking for unbalanced chromosome abnormalities and balanced chromosome rearrangements, which involve small pieces of chromosomes. These chromosome abnormalities may not be found by using our current testing methods. Therefore, for this study, we are using new test methodologies to find subtle chromosome abnormalities.

The following sub-study is included in this research.

Genotype/Phenotype Database

A genotype/phenotype database for individuals with an unbalanced telomere or centromere abnormality is under development. No personal identifiers will be included in the database. Therefore, the database will be available via the web for use by professionals and families.