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Genetic Testing For Huntington's Disease

Introduction

As a recognized HDSA Center of Excellence, our goal is to provide comprehensive clinical services to our patients and their family members in the New York City Metropolitan area. One aspect of those clinical services includes genetic counseling and testing services.

The mission of the genetic counseling and testing program is to provide an environment with the necessary support and information such that individuals may make an informed decision regarding presymptomatic genetic testing for Huntington's disease, confirmatory genetic testing for people with symptoms and preimplantation diagnosis and in-vitro fertilization services for family planning. In addition, it is our aim to facilitate the follow-up care of individuals who complete the testing process by referring them to the resources available in the Huntington's Disease Center at Columbia University.

Columbia University HD Testing Faculty and Staff

Neurology
Karen Marder, MD, MPH
Elan Louis, MD, MSc
Sara Janicki, MD

Psychiatry
Mark Groves, MD

Social Work
Deborah Zeck Thorne, LCSW

Genetics
Jill Goldman, MS

IVF
Wendy Chung, MD, PhD

Contact Information

For more information regarding genetic testing for Huntington's Disease contact Jill Goldman, Genetic Counselor at (212)305-7382 or jg2673@cumc.columbia.edu.

Basic Genetics

Heredity is the passing of characteristics from parent to child by genes.

Genes are the basic units of heredity passed from a parent to a child. The genes determine the characteristics of each person. For example, there are genes that affect eye color, hair color and blood type. People differ in these characteristics because their genes are different. There are approximately 100,000 genes that make up the characteristics of a person.

Chromosomes are the packages that carry the genes. Chromosomes are found in every cell of the body and occur in pairs. One copy of each chromosome is inherited from a person's mother and a second copy from the father. Therefore, a person has 2 copies of each chromosome and 2 copies of each gene, one gene on each chromosome. There are many genes on each chromosome.

The DNA code is the basic unit of chromosome information that determines the makeup of the genes. This chemical code makes a gene, and any changes to this code may also change how the gene works. DNA consists of 4 small elements called bases. These bases are named adenine (A), guanine (G), thymine (T), and cytosine (C).

HD Genetics

The gene that causes HD has an area in which 3 bases (CAG) are repeated many times.

1 2 3 4 5 6 7 8 9 10 11 12
CAG-CAG-CAG-CAG-CAG-CAG-CAG-CAG-CAG-CAG-CAG-CAG.

The gene for Huntington's disease is located on chromosome number 4. The gene causing HD has 40 or more CAG repeats.

No. of CAG Repeats Outcome
<26 Normal range; individual will not develop HD
27-35 Individual will not develop HD, but the next generation is at risk
36-39 Some, but not all, individuals will develop HD; next generation is also at risk
>40 Individual will develop HD

Genetic testing analyzes the number of CAG repeats on the gene inherited from the individual's mother and the gene inherited from the individual's father. A small blood sample is required for the genetic test.

See HDSA Genetic Testing Guidelines

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Columbia University Medical Center : Department of Neurology : Last updated 03-Nov-2014