Chapter 4 Post

Tay-Sachs Disease


A child with Tay-Sachs disease

Tay-Sachs disease is a genetic disorder caused by the absence of a vital enzyme called hexosaminidase A, abbreviated as Hex-A. Hexosaminidase helps break down gangliosides, a chemical found in nerve tissue. The lack of gangliosides, specifically ganglioside GM2, causes build up in cells. This especially includes nerve cells in the brain.


Tay-Sachs is caused by a defective gene on chromosome 15. Tay-Sachs is a recessive gene, so it can only be developed if both parents carry the gene. If both parents carry the gene, the child has a 25% chance of having Tay-Sachs. If only one parent carries the gene, the child may be a carrier.


Anyone can be a carrier of Tay-Sachs disease, but it is most common in the Ashkenazi Jewish population. There are three forms of Tay-Sachs; classic infantile, juvenile, and late onset. The most common of these is classic infantile, when nerve damage begins when the baby is in the womb.  Symptoms appear when the child is 3-6 months old, and quickly gets worse. In this situation, the child usually dies by age 4-5.


Unfortunately, there is currently no treatment and no way to prevent this deadly disease. However, you can get genetic testing to detect whether you are a carrier for the disorder.

A karyotype of an individual with Tay-Sachs disease

Article link: Tay-Sachs Disease
National Tay-Sachs & Allied Disease's Website: NTSAD.org




Beyond the Signal Sequence: Protein Routing in Health and Disease

So, this article was very long! After spending an hour and not even getting through an eighth of it, I think I will save the full reading for another time.

It all started in 1971 when Gunter Blobel proposed the "signal hypothesis." Blobel speculated there is a fundamental signal that governs protein movement across membranes. Blobel and others consequently revealed other "address tags" that direct proteins to intracellular organelles. These principles are universal, operating similarly in yeast, plant, and animal cells. Blobel's work was recognized in 1999 with a Nobel Prize in "Physiology or Medicine." Recent evidence, based from mutations that result in human disease, led to another conclusion: "the successful intracellular routing of many proteins is also governed by a sensitive quality control (QC) system that recognizes particular structural motifs, then retains and degrades defective molecules". Abnormal proteins are very dangerous to cells because they interfere with normal functions and may result in cell death.

Gunter Blobel

The article continues on to describe protein processing and the role of chaperones, diseases caused by defective routing, diseases caused by conformation errors, and rescue of defective proteins.


Article Link: Beyond the Signal Sequence


Useful Material: Cell Organelles YouTube Video

WARNING: this video is extremely lame! And I doubt the song will become a Top 40's hit, but that's not the point. It explains the major organelles (vacuoles, nucleus, golgi, ER, chloroplasts, etc.) and their functions. I find this kind of similar to the "atom video" we saw in freshman year biology. So if you chose to watch the video, the chorus will probably become stuck in your head. My whole family found this out the hard way. Rhymes always help me retain information better, so hopefully it will help you too!

"Cells, cells, they're made of organelles. Try to pull a fast one, the cytoplasm gels. The nucleus takes over, controlling everything. The party don't stop 'till the membrane blocks the scene."