Genes: The Basic Concept Of Genetic Disorder

Approximately three to four percent of babies born every year are born with some kind of genetic disorder. A genetic disorder is described as an illness caused by an error in one’s genome, and is usually hereditary. To understand how these errors occur, one must first understand the basic concept of genes. Genes are the basic units of heredity and are made up of pieces of DNA that instruct the cell how to make specific proteins. Humans are estimated to have about 20,000 to 30,000 genes in their genome. Chromosomes contain these genes and DNA. Humans have 23 pairs of chromosomes or a total of 46 chromosomes. One pair of these chromosomes determines the sex of a person while the other 22 are autosomal, meaning that they determine the rest of the body’s traits, both genetic and phenotypic. Sometimes mutations occur in the genes of the chromosomes which could lead to a genetic disorder or could be perfectly harmless. Other times they happen from the chromosomes themselves if the chromosome breaks off, switches with another part of a chromosome, or is swapped within the same chromosome. This leads to mutation in gene coding and could potentially cause genetic disorders. There are different types of genetic disorders that each cause different kinds of diseases. Genetic disorders arise from chromosomal abnormalities, single gene defects, multifactorial problems, and teratogenic problems.

Chromosomal abnormalities occur when there is an anomaly in chromosome number or structure. The two main types of chromosomal abnormalities are numerical abnormalities and structural abnormalities. Examples of numerical abnormalities are monosomies which is when a chromosome is missing from a chromosome pair and trisomies which is when there is an ext...

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...known as balanced translocation is when segments of chromosomes have been exchanged, however nothing is lost or added. A Robertsonian translocation is similar to a reciprocal translocation except that one chromosome attaches to the centromere of another. In an inversion, part of a chromosome has broken off, been turned upside down, and has reattached to itself. Lastly, in a ring, a portion of a chromosome has been broken off and forms circle. Usually these structural abnormalities are due to an accident in one of the gametes, and therefore are also present in all of the body’s cells. However, in some instances, these abnormalities occur after conception, resulting in mosaicism, in which some cells have the abnormality where others do not. In general, chromosomal abnormalities are either inherited or be “de novo” which means they are new to that specific individual.