Genetics and Evolution Coursework Essay

What is Tay-Sachs Disease?

Tay-Sachs disease is an autosomal recessive fatal genetic disorder that destroys nerve cells in the brain and spinal cord progressively Which is also known as GM2 gangliosides or hexosaminidase-A (Hex-A) disorder. According to literature the absence of Hex-A, a fatty substance, or lipid, called GM2 ganglioside will accumulate abnormally in cells, especially in the nerve cells of the brain.

The disease was named by two doctors working independently; Warren Tay (183-1927) British ophthalmologist, who in 1881 described a patient with cherry-red spot on retina of the eye.

And Bernard Sachs (1858-1944), an American neurologist whose spend several years later provided the first description of the cellular change in Tay-Sachs, moreover he identify (acknowledge) the familial nature of the disease, and, by observing several cases he noted that the higher occurrence of Tay-Sachs disease in Jews of eastern and central European descent, but many cases now occur in people from different ethnic backgrounds.

Hex-A Deficiency Discovered and Gene Identify:

In August 1969 both Dr. Shintaro Okada and Dr. Johns. O’Berien announced the discovery of the Hexosaminidase A deficiency in Tay-Sachs. About two years later in May 1971 the first screening of the Tay-Sachs disease took place in Bethesda, Maryland. The gene that causes the disease was recognized in late 1980’s and by the mid-1990’s, more than 75 different mutation had been identified, until this day there are over 100 mutations been reported from the ethnic group.

Tay-Sachs and Genetics

Basically, Tay-Sachs disease genetically inherited which causes a neurodegenerative disorder. Individuals who affected from this disease experience abnormal brain development that gets progressively worse. The consequences are a life expectancy of no more than five years of age due to complexity related to this disorder such as (pneumonia)

Tay-Sachs disease is inherited from one’s parents, who do not show any symptoms. The disease(the condition) is an autosomal recessive disorder. Put another way, the parents have a defective gene but because the gene has not been expressed, they do not have symptoms. However, if both parents who have a defective gene produce a child, the child ability to inherit both copies of the defective gene will be more, one from each parent and what will happen is the child will express the disease.

The defective gene produces a protein, specifically an enzyme called hexosaminidase A (Hex-A) which is located 15q23, which is the long (q) arm of chromosome 15 at position 23 as it shows in (Figure 1).

(Hex-A) is essential for speeding up a certain biochemical reaction as its been mentioned before the enzyme disorder leads to the accumulation of a compound called ganglioside GM2, a fatty lipid or substance found enriched in nerve cells of the brain. This compound accumulation in the brain leads to the deterioration(failure) of both physical and mental development.

Muscular degeneration will impact children who over the time they will become blind, deaf, and unable to swallow any food which could lead to complete paralysis. The main reasons why Tay-Sachs become worse more and more with age because the compound retain accumulating over the time. This fatty substance can even accumulate during pregnancy, where the first destructive effect take place, although the clinical significance dose not appear until the first few months after birth.

Symptoms:

Tay-Sachs symptoms disease usually start when a child is 3 to 6 months of age which is heartbreaking. Around this time, the slowing in baby developments and the muscles weaken will be noticed. Progressively, the disease will cause more symptoms in infants such as :

• A loss of motor skills such as sitting, turning over, crawling basically losing skills they already learnt.
• A strong reaction to loud noises
• Trouble focusing on objects or even following with their eyes
• Cherry-red spots, which can be seen clearly with an eye examination, in the eyes.

More symptoms will appear by age 2, most children with Tay-Sachs will face more severe issues including :

• Difficulty swallowing
• Breathing problems keep getting worse and worse
• Loss of vision, hearing
• Loos of mental function

Which will eventually lead to paralysis.

How It’s Inherited:

While anyone could be a carrier of Tay-Sachs disease, meaning both parents have a defective copy of the gene (Figure 2), which causing a fault in child’s gene and that prevent the nerves from working properly, the incidence of Tay-Sachs disease is significantly higher between people from eastern European (Ashkenazi) Jewish descent.

Roughly one in every 27 Jews in the United States is a carrier of the disease gene, more over Non-Jewish French Canadians who are living near the St. Lawrence River and in Cajun Community of Louisiana also have a higher incidence of Tay-Sachs, and Old Order Amish community in Pennsylvania, as it has been mentioned before the disease occur in people from different ethnicity so for the general population, about one in 250 people are carriers.

Is There a Cure for Tay-Sachs Disease?

While researchers are still looking for a way to prevent this disease, unfortunately currently there is no cure exists for Tay-Sachs disease however there is kind of treatment but just to make living with it as comfortable as possible. This is called ‘palliative care’, and the process will be, children’s with Tay-Sachs disease will be transferred to a team of specialists, as will help to come up with a perfect plan for those children’s.

Treatments may include:

• Medicines. To help reduce these child’s symptoms, medications will be available for them, including anti-seizure, stiffness medications and Antibiotics to treat any kind of infections like pneumonia if they occur.
• Physiotherapy. Children’s with Tay-Sachs disease are more likely to have a lung infection that cause breathing problems and frequently accumulate mucus in their lunges so to reduce the risk of pneumonia and help with stiffness and improve coughing physiotherapy will be provided.
• Feeding tubes. Children with Tay-Sachs disease may face issue with swallowing or develop respiratory problems by sniffing food or liquids in the lungs while eating. Doctors may require an assistive feeding device to such as gastrostomy to prevent these issues.
• Physical therapy. As the disease progresses, children’s need to keep joints flexible to maintain as much ability to move as possible that’s why physical therapy will be there to help them.
• Support. One of the most important is supporting the family emotionally, seeking out support groups could help them to cope.
• Play and stimulation. It can help those child’s interact with the world through music, scents, and textures.
• Palliative and hospice care. These programs help manage quality of life for children with Tay-Sachs and their families.

How Is Tay-Sachs Diagnosis?

There is a particular way to prevent the community from having babes with Tay-Sachs disease. From a simple blood test can identify Tay-Sachs. Blood samples can be analyzed by ether enzyme assay or DNA studies before the pregnancy it possible to determine whether both or one of the partners are carriers. The gene that cause Tay-Sachs disease. If both partners carry the gene, they might see a genetic counselor to know more about the sequences, then they can decide whether to start a family.

When women is already pregnant, there is two tests that can be performed during the pregnancy period to determine whether the baby will have Tay-Sachs disease.

Chorionic villus sampling (CVS): this test should be done between 10th and 12th weeks of pregnancy by putting a thin needle into belly or places a tube through vagina into cervix, then a small piece will be taken  of the tissue from placenta, the organ that gives the baby nutrients and oxygen. The tissue will be sent to the lab to be tested.

Amniocentesis: this test had to be done bet  ween 15th and 19th weeks of pregnancy, same process as chorionic villus sampling but the sample will be taken from amniotic fluid, the fluid that surrounds the baby in the womb. The fluid will be sent to the lab and tested whether the baby has Tay-Sachs.

Even after giving pregnancy a blood test can show whether the baby got the Hex-A enzyme. Babies who are missing this enzyme have Tay-Sachs also eye exam could determine if the baby has got the disease by looking for a red spot in macula , a part of retina in the back of the eye.