Chromosome 15 Change Disorders

Chromosomes are DNA molecules within cells and within these threadlike structures are coils of proteins that support the purpose and function of the cell. Each person has 46 chromosomes which amount to 23 pairs. Chromosomes are blueprints for growth and for the future activity of the growing and active person.

Chromosome 15 is made up of possibly a million DNA building blocks—proteins are the building blocks of the human body—and comprises about a third of all DNA in genes, the actual role players in the makeup of the body. This particular chromosome contains anywhere from 650 to 1000 genes. Scientific researchers who know and are learning about this area of genetic research have found specific chromosomal disorders that possibly are responsible for some inherited conditions. Among this group are:

 *Acute promyecytic leukemia is a cancerous blood condition that is caused by alterations in gene 15 and in gene 17. T(15;17 results when genetic material from a PMLgene—located on chromosome 15— becomes entangled with RARAgene from chromosome 17. This however is not a genetically inherited disease, but a somatic mutation that happens sometimes during the lifetime of the person.

This disease results because the normal cancer cell growth is prohibited by the protein that is produced by this irregular meeting between chromosome 15 and 17. The normal activity of cell production is interrupted and allows for an excess of promyelocytes in the bone marrow and white blood cells cannot form.

*Angelman syndrome happens with a lowered amount of activity in chromosome 15 in each of its cells. The long q arm of the chromosome, 15q11-q13 is home to a gene labeled UBE3A that possibly is responsible for this abnormality. People ordinarily get one copy of the UBE3A gene from each set of a parent, but in this disease things have gone awry. In Angelman syndrome the brain area that generates the activity of this gene is turned off and only a copy received inherently from a mother is used. The process of this “parent-specific gene activation” is labeled genomic imprinting. When a copy of the mother’s gene is lost because of some abnormality or a mutation, a weakness occurs. This is an inherited condition, unlike the specific type of leukemia described above.

*Prader-Willi syndrome is also caused by loss of genes of Chromosome 15. The same area of the long arm of the Chromosome 15, 15q11-q13 is where the loss originates. The differentiation between the two has to do with the type of genes involved. In this case, however, the missing link is genes from the paternal side of the inheritance. They will have inherited two copies from their mothers and none from their fathers.

*Sensorineural deafness and male infertility too are caused by absences of genes on the long (q) arm of chromosome 15. Hearing loss is associated with STRC; sperm disorder is caused due to a loss of a gene labeled CATSPER2. Men with this abnormality cannot become fathers.

Losses and abnormalities in chromosome 15 can interfere with how a child grows and how they develop. Sometimes and for some unknown reason a change, an inverted duplication of 15 will result in developmental problems, epilepsy and in behavior, an inability to learn, autism, social skills and the ability to effectively communicate.

It is safe to say that most of the health and developmental problems humanity face has an origin in their chromosomes and that a great many of these can be pinpointed to chromosome 15. Scientists are busy at work detecting as many of these abnormalities as they can detect and tomorrow looks brighter and more efficient because of their effort.