The Y sex chromosome of men will not become extinct, according to a study published on Wednesday in the journal Nature. Researchers compared the chromosomes of humans to a Rhesus monkey, a species that separated from human ancestors 25 million years ago, and to chimpanzees, which separated 6 million years ago. The data show that the genetic decay in the Y chromosome was quick at first, but then became minimal in recent history - there is no further gene lost within the past 6 million yeard. "The Y is not going anywhere and gene loss has probably come to a halt. The genes (in Y chromosome) that remain on it have critical biological functions, and that means they are going to survive," said Jennifer Hughes from the Whitehead Institute in Cambridge, Massachusetts, the United States. "We can't rule out the possibility it could happen another time, but the genes which are left on the Y are here to stay," she added. The finding challenged the previous researches which suggested the Y chromosome may become extinct in five million years' time, based on the rate at which genes are disappearing from the chromosome.
Mar 5, 2012
Y chromosome not to become extinct
UK animal-human hybrid embryos trigger controversy in world
News of animal-human hybrid embryos in UK has caused a stir all around the world, according to a report of British newspaper Daily Mail. 155 "admixed" embryos, containing both human and animal genetic material, have been created since the introduction of the 2008 Human Fertilisation Embryology Act, Daily Mail said. Although the scientific sensation has drawn controversy around the UK, this kind of experiments are licensed in this country. The 2008 Human Fertilisation and Embryology Act legalized the creation of a variety of hybrids, including the creation of "cybrids" in which a human nucleus is implanted into an animal cell. Following are several stills from the U.S. movie "Splice" of 2009:
A still from the U.S. movie "Splice" of 2009 (Photo Source:Chinadaily.com)
A simple method for DNA extraction from formalin-fixed, paraffin embedded tissue blocks
Tissue preparation Deparaffinization method Xylene removal To remove the residual xylene, the samples were washed five times with Ethanol as follows. Tissue lysis Phenol-cholorophorm method For the DNA extraction from cell lysate, phenol-chloroform was used as following. References
The microtubes were then left in a 40 ºC oven to dry the tissues.
DNA reveals Neanderthal extinction clues
Neanderthals were already on the verge of extinction in Europe by the time modern humans arrived on the scene, a study suggests. DNA analysis suggests most Neanderthals in western Europe died out as early as 50,000 years ago - thousands of years before our own species appeared. A small group of Neanderthals then recolonised parts of Europe, surviving for 10,000 years before vanishing. The work is published in the journal Molecular Biology and Evolution. An international team of researchers studied the variation, or diversity, in mitochondrial DNA extracted from the bones of 13 Neanderthals. This type of genetic information is passed down on the maternal line; because cells contain multiple copies of the mitochondrial genome, this DNA is easier to extract from ancient remains than the DNA found in the nuclei of cells. The fossil specimens came from Europe and Asia and span a time period ranging from 100,000 years ago to about 35,000 years ago. The scientists found that west European fossils with ages older than 48,000 years, along with Neanderthal specimens from Asia, showed considerable genetic variation. But specimens from western Europe younger than 48,000 years showed much less genetic diversity (variation in the older remains and the Asian Neanderthals was six-fold greater than in the western examples). In their scientific paper, the scientists propose that some event - possibly changes in the climate - caused Neanderthal populations in the West to crash around 50,000 years ago. But populations may have survived in warmer southern refuges, allowing the later re-expansion. Low genetic variation can make a species less resilient to changes in its environment, and place it at increased risk of extinction. "The fact that Neanderthals in Europe were nearly extinct, but then recovered, and that all this took place long before they came into contact with modern humans, came as a complete surprise," said lead author Love Dalen, from the Swedish Museum of Natural History in Stockholm. "This indicates that the Neanderthals may have been more sensitive to the dramatic climate changes that took place in the last Ice Age than was previously thought." Neanderthals were close evolutionary cousins of modern humans, and once inhabited Europe, the Middle East and Central Asia. The reasons behind their demise remain the subject of debate. The appearance of modern humans in Europe around the time of the Neanderthal extinction offers circumstantial evidence that Homo sapiens played a role. But changes in the climate and other factors may have been important contributors. "The amount of genetic variation in geologically older Neanderthals as well as in Asian Neandertals was just as great as in modern humans as a species," said co-author Anders Gotherstrom, from Uppsala University. "The variation among later European Neanderthals was not even as high as that of modern humans in Iceland." The researchers note that the loss of genetic diversity in west European Neanderthals coincided with a climatic episode known as Marine Isotope Stage Three, which was characterised by several brief periods of freezing temperatures. These cold periods are thought to have been caused by a disturbance of oceanic currents in the North Atlantic, and it is possible that they had a particularly strong impact on the environment in western Europe, note the researchers. Over the last few decades, research has shown that Neanderthals were undeserving of their brutish reputation. (BBC) Researchers recently announced that paintings of seals found in caves at Nerja, southern Spain, might date to 42,000 years - potentially making them the only known art created by Neanderthals. However, this interpretation remains controversial.
Neanderthals were close evolutionary cousins of our own species - Homo sapiens
The last Neanderthals might have held out in southern Europe until 24,000 years ago
Were Neanderthals responsible for these cave paintings of seals at Nerja in southern Spain?
'DNA robot' targets cancer cells
Scientists have developed and tested a "DNA robot" that delivers payloads such as drug molecules to specific cells. The container was made using a method called "DNA origami", in which long DNA chains are folded in a prescribed way. Then, so-called aptamers - which can recognise specific cell types - were used to lock the barrel-shaped robot. In lab tests described in Science, the locks opened on contact with cancer cell proteins, releasing antibodies that halted the cells' growth. The method could find wide use in biological applications, where this kind of "specificity" is highly prized. Lead author of the research, Shawn Douglas of the Wyss Institute at Harvard University, said the result brings together several recent research strands. "We've been working on figuring out how to build different shapes using DNA over the past several years, and other researchers have used antibodies as therapeutics, in order to manipulate cell signalling, and yet others have demonstrated that aptamers can be used to target cancer cell types," Dr Douglas told BBC News. "The novel part is really integrating all those different pieces and putting them together in a single device that works." In essence, the approach co-opts a number of strategies of our immune systems, with the robots playing the role of white blood cells that hunt down problematic cells and destroy them. The team tested the robots using several cultures of cancer cells including lymphoma and leukemia, with corresponding payloads of antibodies. Because DNA is found in nearly all of our cells, Dr Douglas said the robots posed fewer problems of toxicity than many materials would have. Scientists have already discovered a large number of different aptamers that can "recognise" proteins corresponding to different diseases, so the approach could in principle be adapted to a wide range of applications. Dr Douglas said that there was still much optimisation to be done on the robots; for now the team will create a great many of them to be tested in an animal model.
The barrel shape opens and spills its payload when the "locks" come into contact with target cells
Mar 4, 2012
New DNA Study Reveals Glacier Mummy's Medical Problems
European scientists say a recently completed DNA map of the Iceman - the well-preserved, 5,300-year-old mummy discovered in a melting Alpine glacier in 1991 - is yielding new details about the man's physical look, his ethnic origins and his health - including an apparent predisposition for heart disease.
The details are described in a new paper by scientists at the European Academy for Mummies and the Iceman in Bolzano, Italy, and at the Institute for Human Genetics in Germany. Among the key findings is that the Iceman, whom scientists have nicknamed Oetzi, was genetically at risk for heart disease, even though he was neither sedentary nor overweight. Researchers say that fact is significant because it shows that the cardiovascular condition existed more than 5,000 years ago, and therefore cannot be associated primarily with modern lifestyles.
In addition to his heart problems, Oetzi’s newly mapped genome reveals that he also suffered from the chronic tick-borne illness, Lyme disease, or borreliosis. The researchers say this is the earliest-known case of the bacterial infection, and provides proof that Lyme disease was present in the New Stone Age period.
Oetzi also was lactose intolerant, meaning he could not digest milk products. The scientists say this finding supports the theory that lactose intolerance - which persists today in most Asians and Africans but affects few northern Europeans - was still a common condition in Oetzi's time, even though his people were becoming increasingly involved in farming and the domestication of dairy animals.
The researchers believe Oetzi’s ancestors likely hailed from the Middle East, and migrated to Europe as agriculture and cattle breeding continued to spread. They say the dwindling populations of modern-day Europeans who share the Iceman’s genetic heritage are found mostly in geographically isolated areas, such as the Mediterranean islands of Sardinia and Corsica.
Oetzi's new DNA map also has helped researchers reconstruct the physical appearance of the ill-fated traveler. They say he had brown eyes and long, wavy brown hair, which scientists believe would have been worn loose. He stood approximately 1.6 meters tall --an average height for a man during the New Stone Age - and he weighed an estimated 50 kilograms.
The analysis of the Iceman’s complete genome is published in the journal Nature Communications.
Earlier studies concluded that Oetzi died at the venerable age of 45. However, later examinations of wounds on the mummy suggested the Iceman was murdered, fatally shot in the back with an arrow and left to die on an Alpine glacier.
Many scientists believe that the high quality of the Iceman’s clothing and items he was carrying when he was killed, such as a fine copper axe, make it likely that Oetzi and his family had considerable social standing within their community.
Oetzi the Iceman's frozen corpse was naturally mummified in the spot where he fell dead, more than 600 years before the first bricks were laid in Giza for Egypt's Great Pyramid. Entombed under a deepening layer of snow and ice, the mummy remained undisturbed until 1991, when two German hikers happened on the partially exposed corpse while trekking through the Oetztal Alps, near the Italian border.
(Source: VOA)
Jul 1, 2011
Chromosome In Situ Hybridization
A modern approach to the specific location of genes on chromosomes is a technique for the hybridization of DNA and RNA "in situ." With this procedure, specific radioactive RNA or DNA (known as probes) can be isolated (or synthesized "in vitro") and then annealed to chromosomes which have been treated in such a manner that their basic double stranded DNA has been "melted" or dissociated.
In theory, and fortunately in practice, when the DNA is allowed to re-anneal, the probe competes for the binding, but only where it mirrors a complimentary sequence. Thus, RNA will attach to the location on the chromosome where the code for its production is to be found. DNA will anneal to either RNA which is still attached to a chromosome, or to the complimentary sequence DNA strand within the chromosome. Since the probe is radioactive, it can be localized via autoradiographic techniques.
Finally, it is possible to produce an RNA probe that is synthesized directly from repetitive sequences of DNA, such as that found within the nucleolar organizer region of the genome. This RNA is known as cRNA (for copied RNA) and is a convenient source of a probe for localizing the nucleolar organizer gene within the nucleus, or on a specific chromosome.
The use of in situ hybridization begins with good cytological preparations of the cells to be studied, and the preparation of pure radioactive probes for the analysis. The details depend upon whether the hybridization is between DNA (probe) and DNA (chromosome), DNA (probe) and RNA (chromosome), or between RNA (probe) and DNA (chromosome).
Preparation of the Probe:
Produce radioactive RNA by incubating the cells to be measured in the presence of 
H-uracil, a specific precursor to RNA. Subsequent to this incubation, extract rRNA from the sample and purify through differential centrifugation, column chromatography or electrophoresis. Dissolve the radioactive RNA probe in 4X Saline-Citrate containing 50% formamide to yield a sample that has 50,000 to 100,000 counts per minute, per 30 microliter sample, as determined with a scintillation counter. Add the formamide is added to prevent the aggregation of RNA.
Preparation of the Slides:
Fix the materials to be studied in either 95% ethanol or in 3:1 methanol:water, attach to pre-subbed slides (as squashes for chromosomes) and air dry.
Hybridization
Place the air dried slides into a moist chamber, usually a disposable petri dish containing filter paper and carefully place 30 microliters of RNA probe in 4X SSC-50% formamide onto the sample.
Carefully add a cover slip (as in the preparation of a wet mount), place the top on the container and place in an incubator at 37° C for 6-12 hours.
Washing:
Pick up the slides and dip into 2X SSC so that the coverglass falls off.
Place the slides in a coplin jar containing 2X SSC for 15 minutes at room temperature.
Transfer the slides to a treatment with RNase (50 microgram/ml RNase A, 100 units/ml RNase T1 in 2X SSC) at 37° C for 1 hour.
Wash twice in 2X SSC, 15 minutes each.
Wash twice in 70% ethanol, twice in 95% ethanol and air dry.
Autoradiography:
Add photographic emulsions to the slides and after a suitable exposure period, develop the slides, counterstain and add cover slips.
Analyze the slides by determining the location of the radioactive probe on the chromosomes or within the nuclei.
(Dr. William H. Heidcamp)
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