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Glossary of Terms Related to Congenital Muscle Disease

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Term Definition
Deletion Mutation

DNA is the genetic language and is read from left to right in 3 letter words. Let us say a normal piece of DNA says “THE MAN HAS CAT AND HAT” . DNA language does not have spaces so in DNA language, above would read: THEMANHASCATANDHAT. In a deletion mutation, one or more letters are removed. For example, if the E in THE was deleted, you would have THMANHASCATANDHAT. When the copying machinery would read it out by 3, it would no longer make sense THM ANH ASC ATA NDH AT.

Deletion/Duplication Analysis

Molecular genetic testing to identify larger size deletions or duplications (typically between 40 basepairs and 40 Kilobases) of DNA within a gene. These methods typically do not detect smaller deletions or duplications of a few base pairs (which can be identified by other methods). Methods used include: array CGH; Multiplex Ligation-dependent Probe Amplification (MLPA); quantitative, real-time, or deletion-specific PCR; or Southern blot

Diagnosis

The specific name of a medical disorder.

DNA

The genetic language. It is contained within the cell’s nucleus in the form of chromosomes. The DNA alphabet is made up of 4 different nucleotides, adenine, guanine, thymine and cytosine, abbreviated AGTC. The genetic language is “read” in triplets so AGT, CTA (much like you read off your credit card number in sets of four, DNA is sets of three). These codons or sets of three are first transcribed into RNA and then encode a particular amino acid that when put next to another amino acid forms a particular protein. Some sets of three represent stop signs or pauses in the reading frame. Sometimes a mutation (or change) in one letter of the DNA alphabet creates a stop sign where an amino acid should be coded. This is one example of a mutation called a nonsense mutation.

Dominant Negative

This describes the mechanism by which a dominant mutation can cause disease. A mutation whose gene product adversely affects the normal (wild type) gene product within the same cell. The mutated copy may associate with the normal copy and cause dysfunction of both. In some cases, such as collagen (Ullrich CMD), one dominant negative mutation may be more harmful than having one mutation causing the production of no gene product (null mutation or null alleles), which only cause disease when present in both gene copies so that absolutely no product can be made.

Dysmotility

When digested food does not move through the stomach or intestines at the right speed. Digested food moves through our body when the muscles in our intestines move like a wave to push the food along. Sometimes the wave moves too slowly and can cause constipation. Other times it moves too quickly and can cause diarrhea.

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