Marker chromosome
An abnormal chromosome that is distinctive in appearance but not fully identified. A marker chromosome is not necessarily a marker for a specific disease or abnormality, but it can be distinguished under the microscope from all the normal human chromosomes. For example, the fragile X (FRAXA) chromosome was once called the marker X.
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- Marker gene
A detectable genetic trait or segment of DNA that can be identified and tracked. A marker gene can serve as a flag for another gene, sometimes called the target gene. A marker gene must be on the same chromosome as the target gene and near enough to it so that the two genes (the marker […]
- Marker, blood
A sign of a disease or condition that can be isolated from a blood sample. For example, the monoclonal antibody D8/17 is a diagnostic sign of pediatric autoimmune disorders associated with streptococcus.
- Marker, tumor
A substance that can be detected in higher-than-normal amounts in the blood, urine, or body tissues of some patients with certain types of cancer. A tumor marker may be made by a tumor itself, or it may be made by the body as a response to the tumor. Tumor marker tests are not used alone […]
- Marmoreal
Resembling marble. For example, the bone in osteoporosis appears marmoreal. From the Latin noun “marmor” meaning “marble.”
- Marriage, cousin
A form of consanguinity. Everyone carries recessive alleles, genes that are generally innocuous in the heterozygous state but that in the company of another gene of the same type are capable of causing disease. We are all genetic reservoirs for genetic disease. Since first cousins share a set of grandparents, for any particular allele (gene) […]