Chromosome 1

Many genetic conditions are related to changes in particular genes on chromosome 1. This list of disorders associated with genes on chromosome 1 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 1.

cancers

Changes in the structure of chromosome 1 are associated with certain forms of cancer and conditions related to cancer. These changes are typically somatic, which means they are acquired during a person's lifetime and are present only in tumor cells.

Deletions in the short (p) arm of the chromosome have been identified in tumors of the brain and kidney. Duplications in the long (q) arm of the chromosome have been reported in a disorder called myelodysplastic syndrome, which is a disease of the blood and bone marrow. People with this condition have a low number of red blood cells (anemia) and an increased risk of developing leukemia.

1p36 deletion syndrome

1p36 deletion syndrome is caused by a deletion of genetic material from a specific region in the short (p) arm of chromosome 1. The signs and symptoms of this disorder, which include intellectual disability, distinctive facial features, and structural abnormalities in several body systems, are probably related to the loss of multiple genes in this region. The size of the deletion varies among affected individuals.

thrombocytopenia-absent radius syndrome

Everyone diagnosed with thrombocytopenia-absent radius (TAR) syndrome, which is characterized by bleeding problems and abnormal development of the forearms, has had a deletion of genetic material on chromosome 1. The deletion removes about 200,000 DNA building blocks (200 kilobases, or 200 kb) from the long (q) arm of the chromosome at position 1q21.1. This section of the chromosome contains 11 genes. The loss of multiple genes in this region is believed to be responsible for TAR syndrome.

Not all people who inherit the deletion of genetic material on chromosome 1 associated with TAR syndrome will develop the disorder. Even within a single family, some people with the deletion may have TAR syndrome while others are unaffected. For this reason, researchers believe that the 1q21.1 200 kb deletion is needed to cause TAR syndrome but that some other, unknown genetic change must also be present.

other chromosomal conditions

Other changes in the number or structure of chromosome 1 can have a variety of effects, including delayed growth and development, distinctive facial features, birth defects, and other medical problems. Changes to chromosome 1 may include an extra segment of the short (p) or long (q) arm of the chromosome in each cell (partial trisomy 1p or 1q), a missing segment of the short or long arm of the chromosome in each cell (partial monosomy 1p or 1q), or a circular structure called ring chromosome 1. 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 1 helpful. These materials are written for the general public.

• Additional NIH Resources - National Institutes of Health
  National Human Genome Research Institute: Chromosome Abnormalities
• 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
• Gene Tests - DNA tests ordered by healthcare professionals (2 links)
• Research Resources - Tools for researchers (8 links)
• PubMed - Recent literature
• OMIM - Genetic disorder catalog (5 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

anemia ; base pair ; birth defect ; bone marrow ; cancer ; cell ; chromosome ; deletion ; DNA ; duplication ; gene ; kb ; kidney ; kilobase ; leukemia ; monosomy ; myelodysplastic syndrome ; red blood cell ; ring chromosomes ; sign ; symptom ; syndrome ; thrombocytopenia ; trisomy ; tumor

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

See also Understanding Medical Terminology.