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Genetic Linkage

Speedy the Tortoise and Altering the Genetic Code

Speedy the tortoise
Last week my sister sent me a great article from Buzzfeed on “a reptile dysfunction”. It’s about stupid people who buy cute little baby tortoises that, after a few sweet months, enter a growth spurt and rapidly begin toassume the dimensions of a dinosaur.

I did that.

An African Tortoise in Upstate New York

I got Speedy, an African spurred tortoise of species Centrochelys sulcata (they have their own closed Facebook group) at a reptile show when she was the size of an oreo. I should have realized that the fact that her natural habitat south of the Sahara was not exactly like that of the northeast US might be a limitation. But it was spring, and Speedy happily munched the lawn for months.

She grew. FastRead More 
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Using the Genetic Code for Passwords

Many years ago, a friend was helping me set up a desktop computer. When the time came to choose a password, he said it should be:

• Alphanumeric
• More than 7 numbers or letters
• Obvious to me, but not to anyone else

The genetic code popped into my mind, and has remained an endless source of diverse passwords, valuable because they may seem nonsensical to non-biologists.  Read More 
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Ricki’s Rant: Genome Sequence, NOT Genetic Code

Strawberries can use a gene from peanuts to withstand frost because the genetic code is universal.
Humans do not have their own genetic code, and certainly each of us does not have his or her own. The idea of our utter uniqueness might be attractive, but genetics just doesn’t work that way. And it’s a good thing.

The genetic code is the correspondence between a unit of DNA  Read More 
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Genetic Sense and Nonsense

Genetic Linkage connects new research findings, based on the wiring of my brain after years of writing a human genetics textbook and lots of articles. Here, the linking of sense and nonsense.

The excitement of genetic research these days is when genome sweeps of people sharing a disease reveal possible responsible genes. That’s what happened when researchers at the Perelman School of Medicine at the University of Pennsylvania looked at genomic landmarks among 1,114 brains from people who had died of progressive supranuclear palsy (PSP), a form of dementia that affects movement.

PSP is a “tauopathy,” in which the dark gummy protein tau, of Alzheimer’s fame, smothers the brain. Compared to unaffected brains, the PSP brains differ in three genome neighborhoods, harboring three new
candidate genes that make sense: one impairs brain cells’ abilities to untangle misfolded proteins, another boots misfolded proteins out of cells, and a third may help wrap brain cells in insulating myelin. New drug targets!

In genetics nonsense is important too. A nonsense mutation inserts a “stop” right smack in the middle of a gene, like a period in the middle of a sentence. It shortens the encoded protein, causing some 1800 diseases. Ignoring a nonsense mutation can restore function, like saving a sentence truncated by an errant period with a stroke of white-out. The idea isn’t new – researchers discovered that bacteria can read-through nonsense mutations in the 1960s, and that certain common antibiotics, such as gentamicin, enable cells to read-through nonsense. Those drugs may provide old-fashioned (cheap) treatments for genetic diseases such as Rett syndrome. Alas, early attempts at treating cystic fibrosis, hemophilia, and Duchenne muscular dystrophy by suppressing nonsense mutations didn’t work because the antibiotic doses necessary would be toxic.

Now Yi-Tao Yu and co-workers at the University of Rochester report in Nature that they have invented a way to mimic antibiotic-mediated nonsense suppression. They’ve used a synthetic RNA to chemically tweak nonsense codons so that they are instead read as bona fide amino acids, in essence altering the genetic code. So far this approach, dubbed RNA modification, works in a test tube. But carefully-directed nonsense suppression holds enormous promise for correcting many genetic diseases. Stay tuned! Read More 
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