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Cancer Genetics

Chromosomes and Cancer

01/09/2001

Question:

1. I've read where a variety of different chromosomes are linked to causing one kind of cancer. Is that because there are different ways to end up with the same disease, or because it isn't known which one is the culprit?

2. Can you explain "loss of heterozygosity" in simple language? I read the definition but I don`t get it. Also, in Layman, what`s "wild type" allele mean?

Answer:

1. Usually only one or two chromosomal changes are linked to actually causing a specific kind of cancer. After a single cell has become cancerous, however, many different chromosomal abnormalities may be seen as a result of the abnormal cell growth pattern.

2. A "wild type" allele is the form of a gene which is normally found in the general population. It is normal in function and structure.

Genes typically occur in pairs. When a person is born with a change or mutation in one of their genes, they have one mutated gene and one wild type gene in the pair. A person is "heterozygous" for that specific gene pair.

If the mutation has occurred in a gene which may predispose to cancer, the next step in the formation of cancer may be the loss of or damage to the normal or wild type gene. If the section of the chromosome containing the gene is actually lost (deleted), we refer to that as "loss of heterozygosity" since the gene pair no longer contains a copy of both versions (alleles).

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Response by:

Judith A Westman, MD Judith A Westman, MD
Associate Professor, Clinical Internal Medicine, Pediatrics and Medical Biochemistry
College of Medicine
The Ohio State University