The influence of genes in diseases is remarkable. There are diseases that are called genetic, including the sickle cell, Duchenne muscular dystrophy, and Down syndrome. These illnesses are caused by genetic variations. On the other hand, diseases such as chicken pox and lung cancer are caused by environmental exposure. Disorders such as certain cancers, dementia, diabetes mellitus, and cardiovascular are triggered both by environmental and genes.
Genetic illnesses are classified as single gene or chromosomal disorders, depending on the particular cause of genes. Disorders that are driven by environmental exposure are multi-factoral. This means, that the diseases are a consequence of interaction or additive effects of non-genetic and genetic factors.
Although many genetic diseases are rare, they are deemed common as a group, and therefore, they are treated by primary care. Having information about the genetic concepts and more common genetic illnesses are helpful to primary care providers in three ways:
First, the information is useful in evaluating the family history, including medical. Second, in differential diagnosis, the genetic disorders are given appropriate consideration. Third, correct use of gene tests and medical genetic services.
Since media is also influential in conveying the information about the diseases, it is significant that genetics is able to distinguish truth from false information. Primary care providers, hence, also benefit from genetics.
Depending on the genetic disease, it can be single-gene or multi-factoral. A few of genetic disorders that are single-gene in nature are breast cancer, mental retardation or cleft palate. Breast cancer develops from mutations in the BRCA1 or BRAC2 gene, while cleft palate is a result of small deletion in chromosome 22. Generally, many of the diseases are multi-factoral, which means, that the diseases are a consequence of combining genetic and non-genetic factors.
Single-gene illnesses are a result of single-gene mutation. No matter how rare some of them are, their frequency varies widely such as from 1/500 to less than 1/50,000.
Knowing about the different patterns of inheritance is helpful as it can make interpretation of family medical history more accurate, and ensures that the genetic testing is administered for best results. The inheritance patterns of single-gene disorders are characterized by two factors. First is the occurrence of disease with one or two copies of mutation. Second is the location of mutation, which can be on the autosome or on sex chromosomes.
Single-gene illnesses follow three patterns of inheritance, namely, autosomal dominant, autosomal recessive, and X-linked recessive. A good example of autosomal dominant is the Huntington disease. Autosomal dominant occurs when the mutation happens in one copy of a gene, even when the other copy is normal.
Autosomal recessive occurs when mutation happens on two copies of the gene. An example of this disease is the sickle cell anemia. Couples who both have similar gene mutations can pass on their genes to children by 25%. The X-linked recessive disorders are those which mutations occur on X chromosome. An example of this is the Duchenne muscular dystrophy.
The multi-factoral disorders happen when there is interaction or addition of genetic or non-genetic factors. Some of these diseases are much known about the influence of both genes and environment, while others are only known for their genetic component. Still, there are a few which are known only for their environmental exposure.
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