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Genetic Linkage

The Covenant of Water by Abraham Verghese: A Geneticist’s Review

The history of genetics begins, not with Gregor Mendel's pea experiments, but with people long ago noticing family resemblances and vulnerabilities so distinctive that shared environment alone can't explain them.

 

In the new literary fiction masterpiece The Covenant of Water, author-physician Abraham Verghese traces an unusual trait through three generations of a Christian family in India, against the historical backdrop of the coalescence of three states into Kerala, on the Malabar Coast, spanning 1900 to 1977. "The family … suffers a peculiar affliction: in every generation, at least one person dies by drowning – and in Kerala, water is everywhere," reads the jacket cover.

 

Through time, the drownings have been ascribed to bad luck and a familial recklessness, rather than to anything as cut in stone as an inherited condition. Frequent drownings seem more coincidence, harder to explain biologically than bleeding from missing a clotting factor or impaired breathing from cystic fibrosis. But the 700+ page tale is indeed about a rare manifestation of a rare condition.

 

The narrative captures the dread of an autosomal dominantly inherited disease, striking every generation, males and females. Dr. Verghese names all of the characters except the patriarch, who passed down the mutation behind the illness that isn't revealed until well into the saga. Perhaps keeping him nameless is a metaphor for the mysterious origin of what the family calls "the Condition."

 

To continue reading, go to DNA Science, where this post first appeared.

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Eclectic Genomics: Cat Flu, Dolphin Adaptation to Climate Change, Predicting Cancer, and Diagnosing Rare Disease

Determining the sequence of building blocks of entire genomes – aka genomics – first came to public attention in the 1990s, with the race to decode the first human genomes. Today, smartphones can carry our personal genome sequences.

 

Genomics applies to all species, revealing evolution in action, because we all use the same genetic code – that is, the correspondence between DNA sequences and the amino acid sequences of proteins. Many popular uses of "genetic code" actually mean "genome sequence."

 

Analysis of environmental DNA (eDNA) catalogs the DNA in specific places, from microorganisms inhabiting a human armpit to vast ecosystems. Several recent DNA Science posts describe eDNA:

 

A Glimpse of The Ocean's "Twilight Zone" Through Environmental DNA
A 2-million-year-old Ecosystem in the Throes of Climate Change Revealed in Environmental DNA
DNA in Strange Places: Hippo Poop, Zoo Air and Cave Dirt
Microbiome Analysis of Ancient Feces

 

Genome sequencing was critical from the start of COVID, as the first SARS-CoV-2 sequences were posted for researchers just days after initial case reports. That information led, thanks to vaccine shelved from the first SARS circa 2003, to the rapid development and deployment of mRNA vaccines against the new infectious disease.

 

To continue reading, go to DNA Science, where this post first appeared.

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A Squishy Sea Creature Regenerates a Body from a Severed Head

Humans aren't very good at regeneration — we can do it for skin, bone, and liver, but that's about it.

 

Flatworms, zebrafish, cockroaches, and salamanders can regenerate entire limbs. Yet even these abilities are unimpressive compared to those of Hydractinia symbiolongicarpus, aka a "squishy sea creature."

 

Only Simpler Animals Regenerate

 

Hydractinia, along with jellyfish, sea anemones, hydra, and  corals, are among 11,000 or so species in phylum Cnidaria, from the Greek cnidos for "stinging nettle." The tiny animals have soft bodies, circular symmetry, and sting. The hydractinia are among the most ancient of the Cnidaria. We last shared an ancestor with these animals more than 600 million years ago. They live in saltwater and are small and tube-shaped, clinging to hermit crabs.

 

To continue reading, go to DNA Science, where this post first appeared. 

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Experiments Reveal the Early Human Embryo, with Implications for Infertility and Early Pregnancy Loss

Several recent reports are filling in the gaps of what we know about the earliest days and weeks of human prenatal development. Rather than attempting to image human embryos, researchers are tracking gene expression – that is, which genes a particular cell turns on or off at a particular time, providing a view of overall function.

 

The early embryos that are being investigated are donated by women undergoing assisted reproductive technologies, or are nurtured from induced pluripotent stem cells, which are created by culturing skin cells (fibroblasts) in a brew of growth factors. The stem cells divide and differentiate into early embryos, but with only partial supportive structures, like the amnion and placenta, so development ceases before the fetal period begins at 8 weeks after fertilization. The stem cells provide a Goldilocks solution, glimpsing early embryos, but not sustaining their development past a few weeks.

 

Three New Reports

 

To continue reading, go to DNA Science, where this post first appeared.

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