Chromosome 17

Many genetic conditions are related to changes in particular genes on chromosome 17. This list of disorders associated with genes on chromosome 17 provides links to additional information.

Changes in the structure or number of copies of a chromosome can also cause problems with health and development. The following chromosomal conditions are associated with such changes in chromosome 17.

cancers

Changes in chromosome 17 have been identified in several types of human cancer. These genetic changes are somatic, which means they are acquired during a person's lifetime and are present only in certain cells. A particular chromosomal abnormality called an isochromosome 17q occurs frequently in some cancers. This abnormal version of chromosome 17 has two long (q) arms instead of one long arm and one short (p) arm. As a result, the chromosome has an extra copy of some genes and is missing copies of other genes.

An isochromosome 17q is commonly found in a cancer of blood-forming tissue called chronic myeloid leukemia (CML). It also has been identified in certain solid tumors, including a type of brain tumor called a medulloblastoma and tumors of the brain and spinal cord known as primitive neuroectodermal tumors. Although an isochromosome 17q probably plays a role in both the development and progression of these cancers, the specific genetic changes related to cancer growth are unknown.

Miller-Dieker syndrome

Miller-Dieker syndrome is caused by a deletion of genetic material near the end of the short (p) arm of chromosome 17. The signs and symptoms of Miller-Dieker syndrome are related to the loss of multiple genes in this region. The size of the deletion varies among affected individuals. The loss of a particular gene on chromosome 17, called PAFAH1B1, is responsible for the syndrome's characteristic sign of lissencephaly, a problem with brain development in which the surface of the brain is abnormally smooth. The loss of another gene, called YWHAE, in the same region of chromosome 17 increases the severity of lissencephaly in people with Miller-Dieker syndrome. Additional genes in the deleted region contribute to the varied features of Miller-Dieker syndrome.

Smith-Magenis syndrome

Most people with Smith-Magenis syndrome have a deletion of genetic material from a specific part of chromosome 17 called the Smith-Magenis syndrome critical region. This region is located on the short (p) arm of chromosome 17 at position 11.2 (written as 17p11.2). Although this region contains multiple genes, researchers believe that the loss of one particular gene, RAI1, in each cell is responsible for most of the physical, mental, and behavioral features of Smith-Magenis syndrome. The loss of other genes in the deleted region may help explain why the signs and symptoms of this condition vary among affected individuals.

other chromosomal conditions

Other changes in the number or structure of chromosome 17 can have a variety of effects, including intellectual disability, delayed development, characteristic facial features, weak muscle tone (hypotonia), and short stature. These changes include an extra piece of chromosome 17 in each cell (partial trisomy 17), a missing segment of the chromosome in each cell (partial monosomy 17), and a circular structure called a ring chromosome 17. Ring chromosomes occur when a chromosome breaks in two places and the ends of the chromosome arms fuse together to form a circular structure.

Geneticists use diagrams called ideograms as a standard representation for chromosomes. Ideograms show a chromosome's relative size and its banding pattern. A banding pattern is the characteristic pattern of dark and light bands that appears when a chromosome is stained with a chemical solution and then viewed under a microscope. These bands are used to describe the location of genes on each chromosome.

See How do geneticists indicate the location of a gene? in the Handbook.

You may find the following resources about chromosome 17 helpful. These materials are written for the general public.

• Additional NIH Resources - National Institutes of Health (2 links)
• MedlinePlus - Health information
  Encyclopedia: Chromosome

You may also be interested in these resources, which are designed for genetics professionals and researchers.

• Gene Reviews - Clinical summary (2 links)
• Gene Tests - DNA tests ordered by healthcare professionals (2 links)
• Research Resources - Tools for researchers (6 links)
• PubMed - Recent literature
• OMIM - Genetic disorder catalog (2 links)
• Map Viewer - Genetic maps

The Handbook provides basic information about genetics in clear language.

• What is DNA?
• What is a chromosome?
• How many chromosomes do people have?
• Can changes in chromosomes affect health and development?

These links provide additional genetics resources that may be useful.

• Genetics education
• Human Genome Project
• Resources for Genetic Researchers

base pair ; cancer ; cell ; chromosome ; chronic ; critical region ; deletion ; DNA ; gene ; hypotonia ; isochromosome ; leukemia ; medulloblastoma ; monosomy ; muscle tone ; myeloid ; progression ; ring chromosomes ; short stature ; sign ; stature ; symptom ; syndrome ; tissue ; trisomy ; tumor

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

See also Understanding Medical Terminology.