Posts about dna

Changing Life as We Know It

Update: Independent researchers find no evidence for arsenic life in Mono Lake

NASA has made a discovery that changes our understanding of the very makeup of life itself on earth. I think my favorite scientific discipline name is astrobiology. NASA pursues a great deal of this research not just out in space but also looking at earth based life. Their astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.

photo of Felisa Wolfe-Simon

Felisa Wolfe-Simon processing mud from Mono Lake to inoculate media to grow microbes on arsenic.

Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.

Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

Researchers conducting tests in the harsh, but beautiful (see photo), environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.

“The definition of life has just expanded,” said Ed Weiler, NASA’s associate administrator for the Science Mission Directorate. “As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it.” This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth.

In science such huge breakthroughs are not just excepted without debate, however, which is wise.

Thriving on Arsenic:

In other words, every experiment Wolfe-Simon performed pointed to the same conclusion: GFAJ-1 can substitute arsenic for phosphorus in its DNA. “I really have no idea what another explanation would be,” Wolfe-Simon says.

But Steven Benner, a distinguished fellow at the Foundation for Applied Molecular Evolution in Gainesville, FL, remains skeptical. If you “replace all the phosphates by arsenates,” in the backbone of DNA, he says, “every bond in that chain is going to hydrolyze [react with water and fall apart] with a half-life on the order of minutes, say 10 minutes.” So “if there is an arsenate equivalent of DNA in that bug, it has to be seriously stabilized” by some as-yet-unknown mechanism.

It is sure a great story if it is true though. Other scientists will examine more data and confirm or disprove the claims.

“We know that some microbes can breathe arsenic, but what we’ve found is a microbe doing something new — building parts of itself out of arsenic,” said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team’s lead scientist. “If something here on Earth can do something so unexpected, what else can life do that we haven’t seen yet?”
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Variation in Human DNA

Variation on the order of thousands to hundreds of thousands of DNA’s smallest pieces – large swaths varying in length or location or even showing up in reverse order – appeared 4,205 times in a comparison of DNA from just four people.

Those structural differences popped into clear view through computer analysis of more than 500 linear feet of DNA molecules analyzed by the powerful genome mapping system developed over nearly two decades by David C. Schwartz, professor of chemistry and genetics at UW-Madison.

“We probably have the most comprehensive view of the human genome ever,” Schwartz says. “And the variation we’re seeing in the human genome is something we’ve known was there and important for many years, but we haven’t been able to fully study it.”

To get a better picture of those structural variations, Schwartz and his team developed the Optical Mapping System, a wholly new type of genome analysis that directly examines millions of individual DNA molecules.

“Our newer genome analysis systems, if commercialized, promise genome analysis in one hour, at under $1,000,” Schwartz says. “And we require that high speed and low cost to power the new field of personal genomics.”

Read full press release

Related: New Understanding of Human DNAOpossum Genome Shows ‘Junk’ DNA is Not JunkBacteria Can Transfer Genes to Other BacteriaScientists crack 40-year-old DNA puzzle

Sumatran Tiger and Cubs Filmed by Remote Wildlife Monitoring Cameras

Video cameras installed in the Sumatran jungle in Indonesia have captured close-up footage of a tiger and two cubs. This is the first time that the World Wildlife Fund has recorded evidence of tiger breeding in central Sumatra in what should be prime tiger habitat.

The Sumatran Tiger is the smallest of all surviving tiger subspecies. Male Sumatran tigers average 204 cm (6 feet, 8 inches) in length from head to tail and weigh about 136 kg (300 lb).

Analysis of DNA is consistent with the hypothesis that the Sumatran Tigers have been isolated after a rise in sea level at the Pleistocene to Holocene border (about 12,000-6,000 years ago) from other tiger populations. The Sumatran Tiger is genetically isolated from all living mainland tigers.

Wouldn’t it be nice to see the photos those tigers could take with the awesome cat cam?

Related: Bukit Tiga Puluh National ParkUsing Cameras Monitoring To Aid Conservation EffortsRare Saharan Cheetahs PhotographedJaguars Back in the Southwest USA

Microcosm by Carl Zimmer

cover of Microcosm by Carl Zimmer

Microcosm: E. Coli and the New Science of Life by Carl Zimmer is an excellent book. It is full of fascinating information and as usual Carl Zimmer’s writing is engaging and makes complex topics clear.

E-coli keep the level of oxygen low in the gut making the resident microbes comfortable. At any time a person will have as many as 30 strains of E. coli in their gut and it is very rare for someone ever to be free of E. coli. [page 53]

In 1943, Luria and Delbruck published the results that won them the 1969 Nobel Prize in Physiology or Medicine in which they showed that bacteria and viruses pass down their traits using genes (though it took quite some time for the scientific community at large to accept this). [page 70]

during a crisis E coli’s mutation rates could soar a hundred – or even a thousandfold… Normally, natural selection favors low mutation rates, since most mutations are harmful. But in times of stress extra mutations may raise the odds that organisms will hit on a way out of their crisis… [alternatively, perhaps] In times of stress, E coli. may not be able to afford the luxury of accurate DNA repair. Instead, it turns to the cheaper lo-fi polymerases. While they may do a sloppier job, E coli. comes out ahead [page 106]
Hybridization is not the only way foreign DNA got into our cells. Some 3 billion years ago our single-celled ancestors engulfed oxygen-breathing bacteria, which became the mitochondria on which we depend. And, like E. coli, our genomes have taken in virus upon virus. Scientists have identified more than 98,000 viruses in the human genome, along with our mutant vestiges of 150,00 others… If we were to strip out all our transgenic DNA, we would become extinct.

I highly recommend Microcosm, just as I highly recommend Parasite Rex, by Carl Zimmer.

Related: Bacteriophages: The Most Common Life-Like Form on EarthForeign Cells Outnumber Human Cells in Our BodiesAmazing Designs of LifeAmazing Science: RetrovirusesOne Species’ Genome Discovered Inside Another’s

Science Explained: RNA Interference

Explained: RNA interference

Every high school biology student learns the basics of how genes are expressed: DNA, the cell’s master information keeper, is copied into messenger RNA, which carries protein-building instructions to the ribosome, the part of the cell where proteins are assembled.

But it turns out the picture is far more complicated than that. In recent years, biologists have discovered a myriad of other molecules that fine-tune this process, including several types of RNA (ribonucleic acid). Through a naturally occurring phenomenon known as RNA interference, short strands of RNA can selectively intercept and destroy messenger RNA before it delivers its instructions.

Double-stranded RNA molecules called siRNA (short interfering RNA) bind to complementary messenger RNA, then enlist the help of proteins, the RNA-induced silencing complex. Those proteins cleave the chemical bonds holding messenger RNA together and prevent it from delivering its protein-building instructions.

This article from MIT is one, of many, showing MIT’s commitment to science education of the public. Good job, MIT.

Related: Antigen Shift in Influenza VirusesPosts explaining scientific principles and conceptsDNA Passed to Descendants Changed by Your LifeWhy Does Hair Turn Grey as We Age?Amazing Science: Retroviruses

2009 Nobel Prize in Chemistry: the Structure and Function of the Ribosome

graphic image of the components of a cellCross section of a cell by the Royal Swedish Academy of Sciences. A ribosome is about 25 nanometters (a millionth of a millimeter) in size. A cell contains tens of thousands of ribosomes.

The Nobel Prize in Chemistry for 2009 awards studies of one of life’s core processes: the ribosome’s translation of DNA information into life. Ribosomes produce proteins, which in turn control the chemistry in all living organisms. As ribosomes are crucial to life, they are also a major target for new antibiotics.

This year’s Nobel Prize in Chemistry awards Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath for having showed what the ribosome looks like and how it functions at the atomic level. All three have used a method called X-ray crystallography to map the position for each and every one of the hundreds of thousands of atoms that make up the ribosome.

Inside every cell in all organisms, there are DNA molecules. They contain the blueprints for how a human being, a plant or a bacterium, looks and functions. But the DNA molecule is passive. If there was nothing else, there would be no life.

The blueprints become transformed into living matter through the work of ribosomes. Based upon the information in DNA, ribosomes make proteins: oxygen-transporting haemoglobin, antibodies of the immune system, hormones such as insulin, the collagen of the skin, or enzymes that break down sugar. There are tens of thousands of proteins in the body and they all have different forms and functions. They build and control life at the chemical level.

Related: The Nobel Prize in Chemistry 20082007 Nobel Prize in Chemistry2006 Nobel Prize in Chemistryposts on chemistrybasic research posts

Details from the Nobel Prize site (which continues to do a great job providing scientific information to the public openly).
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2009 Nobel Prize in Physiology or Medicine

This year’s Nobel Prize in Physiology or Medicine is awarded to three scientists who have solved a major problem in biology: how the chromosomes can be copied in a complete way during cell divisions and how they are protected against degradation. The Nobel Laureates have shown that the solution is to be found in the ends of the chromosomes – the telomeres – and in an enzyme that forms them – telomerase.

The long, thread-like DNA molecules that carry our genes are packed into chromosomes, the telomeres being the caps on their ends. Elizabeth Blackburn and Jack Szostak discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation. Carol Greider and Elizabeth Blackburn identified telomerase, the enzyme that makes telomere DNA. These discoveries explained how the ends of the chromosomes are protected by the telomeres and that they are built by telomerase.

If the telomeres are shortened, cells age. Conversely, if telomerase activity is high, telomere length is maintained, and cellular senescence is delayed. This is the case in cancer cells, which can be considered to have eternal life. Certain inherited diseases, in contrast, are characterized by a defective telomerase, resulting in damaged cells. The award of the Nobel Prize recognizes the discovery of a fundamental mechanism in the cell, a discovery that has stimulated the development of new therapeutic strategies.

Scientists began to investigate what roles the telomere might play in the cell. Szostak’s group identified yeast cells with mutations that led to a gradual shortening of the telomeres. Such cells grew poorly and eventually stopped dividing. Blackburn and her co-workers made mutations in the RNA of the telomerase and observed similar effects in Tetrahymena. In both cases, this led to premature cellular ageing – senescence. In contrast, functional telomeres instead prevent chromosomal damage and delay cellular senescence. Later on, Greider’s group showed that the senescence of human cells is also delayed by telomerase. Research in this area has been intense and it is now known that the DNA sequence in the telomere attracts proteins that form a protective cap around the fragile ends of the DNA strands.

Many scientists speculated that telomere shortening could be the reason for ageing, not only in the individual cells but also in the organism as a whole. But the ageing process has turned out to be complex and it is now thought to depend on several different factors, the telomere being one of them. Research in this area remains intense.

The 3 awardees are citizens of the USA; two were born elsewhere.
Read more about their research at the Nobel Prize web site.

Molecular biologist Elizabeth Blackburn–one of Time magazine’s 100 “Most Influential People in the World” in 2007–made headlines in 2004 when she was dismissed from the President’s Council on Bioethics after objecting to the council’s call for a moratorium on stem cell research and protesting the suppression of relevant scientific evidence in its final report.

Related: Nobel Prize in Physiology or Medicine 20082007 Nobel Prize in Physiology or Medicine2006 Nobel Prize in Physiology or Medicine

Webcast of Dr. Elizabeth Blackburn speaking at Google:
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Extinct Ibex is Resurrected by Cloning

Extinct ibex is resurrected by cloning

The Pyrenean ibex, a form of wild mountain goat, was officially declared extinct in 2000 when the last-known animal of its kind was found dead in northern Spain. Shortly before its death, scientists preserved skin samples of the goat, a subspecies of the Spanish ibex that live in mountain ranges across the country, in liquid nitrogen.

Using DNA taken from these skin samples, the scientists were able to replace the genetic material in eggs from domestic goats, to clone a female Pyrenean ibex, or bucardo as they are known. It is the first time an extinct animal has been cloned.

Sadly, the newborn ibex kid died shortly after birth due to physical defects in its lungs. Other cloned animals, including sheep, have been born with similar lung defects. But the breakthrough has raised hopes that it will be possible to save endangered and newly extinct species by resurrecting them from frozen tissue.

It has also increased the possibility that it will one day be possible to reproduce long-dead species such as woolly mammoths and even dinosaurs.

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Tardigrades In Space (TARDIS)

Research showing that Tardigrades (Water Bears) can survive in space without protection has been in the news lately. There is a blog with a few posts from the research team (only from last year unfortunately): Tardigrades In Space (TARDIS). They chose not to publish the research in an open access fashion, unfortunately.

Tiny Critters Survive Space

These small, segmented animals not only survived a 12-day orbital expedition, some members of the community felled by solar radiation actually recovered upon their return to Earth.

“How these animals were capable of reviving their body … remains a mystery,” said lead researcher Ingemar Jönsson, with Sweden’s Kristianstad University, who writes about the discovery in this week’s issue of Current Biology.

Most of the 3,000 creatures not only survived, but they went on to reproduce once they came back to Earth. About 12 percent of the animals exposed to ultraviolet radiation revived after being put back in water, a puzzling find since researchers presume the sterilizing rays broke down the tardigrades’ DNA. “This type of radiation cuts the DNA strand effectively in most organisms”

Related: Bacteria Frozen for 8 Million Years In Polar Ice ResuscitatedWhat is an Extremophile?posts on extremophiles

Algorithmic Self-Assembly

Paul Rothemund, scientist at Cal Tech, provides a interesting look at DNA folding and DNA based algorithmic self-assembly. In the talk he shows the promise ahead for using biological building blocks using DNA origami — to create tiny machines that assemble themselves from a set of instructions.

Algorithmic Self-Assembly of DNA Sierpinski Triangles, PLoS paper.

I posted a few months ago about how you can participate in the protein folding, with the Protein Folding Game.

Related: Viruses and What is LifeDNA Seen Through the Eyes of a CoderSynthesizing a Genome from ScratchEvidence of Short DNA Segment Self AssemblyScientists discover new class of RNA

DNA Passed to Descendants Changed by Your Life

How your behaviour can change your children’s DNA

Until recently that would also have been the opinion of most scientists. Genes, it was thought, were highly resilient. Even if people did wreck their own DNA through bad diet, smoking and getting fat, that damage was unlikely to be passed to future generations.

Now, however, those assumptions are being re-examined. At the heart of this revolution is a simple but controversial idea: that DNA can be modified or imprinted with the experiences of your parents and grandparents.

According to this new science, known as epigenetics, your ancestors’ diet, smoking habits, exposure to pollutants and levels of obesity could be affecting you today. In turn, your lifestyle could affect your children and grandchildren.

If we drink heavily, take drugs, get fat or wait too long to reproduce, then epigenetics might start tying up some of the wrong genes and loosening the bonds on others. Sometimes those changes will affect sperm and egg cells.

It seems to me this area is still far from having conclusive proof. But it is another great example of scientists seeking to improve our knowledge of how things work.

Related: Nova on EpigeneticsEpigenetics: Sins of the fathers, and their fathersEvidence for Transgenerational Transmission of Epigenetic Tumor Susceptibility in Drosophilaposts on DNA