In certain portions of the Jewish population, there is a genetic disease called Tay Sachs disease, which is fatal to infants within the first five years of life. This disease is caused by a recessive allele of a single gene. Why does this disease persist, even though it is invariably fatal long before the afflicted individual reaches reproductive age
Answers
When two parents reproduce, each parent passes on a complete set of their genes. Therefore, the offspring have two copies of each gene - one inherited from their mother and the other from their father.
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please mark as brainleast
Answer:
Tay Sachs Disease
NORD gratefully acknowledges Michael M. Kaback, MD, Professor, Pediatric & Reproductive Medicine (emeritus), University of California, San Diego School of Medicine, for assistance in the preparation of this report.
Synonyms of Tay Sachs Disease
B Variant GM2-Gangliosidosis
GM2 Gangliosidosis, Type 1
Hexoaminidase Alpha-Subunit Deficiency (Variant B)
Hexosaminidase A deficiency
HEXA deficiency
Sphingolipidosis, Tay-Sachs
TSD
Subdivisions of Tay Sachs Disease
Infantile Tay-Sachs Disease
Juvenile (Subacute) Tay-Sachs Disease
Late-Onset Tay-Sachs Disease
General Discussion
Tay-Sachs disease is a rare, neurodegenerative disorder in which deficiency of an enzyme (hexosaminidase A) results in excessive accumulation of certain fats (lipids) known as gangliosides in the brain and nerve cells. This abnormal accumulation of gangliosides leads to progressive dysfunction of the central nervous system. This disorder is categorized as a lysosomal storage disease. Lysosomes are the major digestive units in cells. Enzymes within lysosomes break down or "digest" nutrients, including certain complex carbohydrates and fats. When an enzyme like hexosaminidase A, which are needed to breakdown certain substances like fats, are missing or ineffective, they build up in the lysosomal. This is called abnormal “storage”. When too much fatty material builds up in the lysosome, it becomes toxic destroying the cell and damaging surrounding tissue.
Symptoms associated with Tay-Sachs disease may include an exaggerated startle response to sudden noises, listlessness, loss of previously acquired skills (i.e., psychomotor regression), and severely diminished muscle tone (hypotonia). Infants with hypotonia may be described as “floppy”. As the disease progresses, affected infants and children may develop cherry-red spots within the middle layer of the eyes, gradual loss of vision, and hearing loss, increasing muscle stiffness and restricted movements (spasticity), eventual paralysis, uncontrolled electrical disturbances in the brain (seizures), and deterioration of cognitive processes (dementia). The classical form of Tay-Sachs disease occurs during infancy. This is the most common form and is usually fatal during early childhood. There are also juvenile and adult forms of Tay-Sachs disease, but these are rare. Children with the juvenile form, also called the subacute form, develop symptoms later than those with the infantile form, and they usually live until later in childhood or adolescence. The adult form, also called late-onset Tay-Sachs disease, may occur anytime from adolescence to the mid-30s. The symptoms and severity can vary from one person to another. Some people may fall in between the juvenile and adult forms.
Tay-Sachs disease is inherited in an autosomal recessive manner. The disorder results from changes (mutations) of a gene known as the HEXA gene, which regulates production of the hexosaminidase A enzyme. The HEXA gene has been mapped to the long arm (q) of chromosome 15 (15q23-q24). There is no cure for Tay-Sachs disease, and the treatment is aimed at relieving the specific symptoms that occur.
Another name for Tay-Sachs disease is GM2 gangliosidosis type 1. There are two other, related disorders, called Sandhoff disease and hexosaminidase activator deficiency that are indistinguishable from Tay-Sachs disease based on symptoms and can only be differentiated through testing to determine the underlying cause. These two disorders are also cause reduced activity of hexosaminidase, but are caused by changes in different genes. Collectively, these three disorders are known as GM2 gangliosidoses.
Signs & Symptoms
Tay-Sachs disease is broken down into the classic or infantile form, the juvenile form, and the adult or late-onset form. In individuals with infantile Tay-Sachs disease, symptoms typically first appear between three and five months of age. In individuals with the late-onset form, symptoms may become apparent anytime from adolescence through the mid-30s.
heritage is a carrier.