Question

Choose only one of these! Discuss the inheritance pattern, populations commonly found in, phenotypes, cellular physiology, and “molecular” stories for: Red-green color blindness, Tay Sachs, Cystic fibrosis, or Hypercholesterolemia.

Please choose one and give detailed info: Red-green color blindness, Tay sachs, Cystic fibrosis or Hypercholesterolemia.

Answer 1

Answer:

Tay Sachs:

Tay Sachs is a rare genetic disorder, that progressively destroys neurons of brain and spinal chord. There are two forms of Tay Sachs seen - infantile and late onset.

Infantile form of Tay Sachs is more common. At birth the child appears normal but by 6 months the Tay Sachs symptoms appear. The weakness of muscles set in and infants lose motor skills. As the muscles used for movement get affected, these infants lose ability to turn, sit and crawl. overall development slows down. As the disease progresses, these infants develop loss of hearing and vision. They also experience seizures and intelligence abilities are lost. Infants thus affected survive only upto few ears into childhood.

Adult form or late onset Tay Sachs is not as severe as infantile version. This too is characterized by loss of movement, speech, hearing and mental illness. The symptoms vary a lot among individuals. Muscle weakness and loss of coordination dominate this form of disease.

Inheritance Pattern:

The disease shows autosomal recessive type of inheritance. This implies that both parents should pass on the recessive gene to the child for the disease to manifest. Those children that inherit only one copy of the gene for one parent only, they become carriers but they don't show any symptoms of Tay Sachs.

Look at the Punnet squares below to understand this inheritance pattern:

The insert shows two case scenarios wherein a normal person marries a carrier - Tay Sachs is not manifested and when two carriers marry, they result in passing down the disorder to roughly 1/4 of their children.

More commonly found in - as mentioned earlier, its a rare disorder and incidence is very low in general population. However, certain communities seem to carry the mutations responsible far more than the general population. These communities include:

• Ashkenazi Jews of eastern and central Europe
• Old Order Amish community of Pennsylvania
• Cajuns of Louisiana
• Certain French-Canadian communities of Quebec

Phenotypes -

As mentioned earlier the disease manifest in muscular loss of movement muscles. In infantile type of Tay Sachs two typical features seen are:

1. Cherry red-spot - an eye abnormality detected on eye examination
2. unusually exaggerated response to certain sounds

Cellular Physiology and molecular manifestation:

Enzyme beta-hexosaminidase is an important enzyme found in the lysosomes of cells, specially neurons. Lysosomes digest and break down any toxic substances in cell. In Tay Sachs there is a mutation in the Hexa gene and that disrupts the function of this enzyme. Due to this disruption enzyme is unable to do its function fully and this in turn leads to accumulation of a fatty substance called GM2 Ganglioside. This substance accumulates specially in neurons of brain and spinal cord. This accumulation results in progressive damage of these neurons and the disease sets in with its manifestations.