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First read this article:
http://www.bbc.co.uk/news/science-environment-23529849
Selfish traits not favoured by evolution, study shows

and then read this... 

Bad DNA can flout rules of inheritance :

R2d2 can quickly spread to an entire mouse population despite its evolutionary disadvantage

In living animals, a selfish bit of DNA called R2d2 is an outright lawbreaker. It violates laws of both genetic inheritance and Darwinian evolution. R2d2 can sweep through mouse populations by mimicking helpful mutations while actually damaging fertility, researchers report online February 15 inMolecular Biology and Evolution.

The new findings suggest that even genes that hurt an organism’s evolutionary chances can cheat their way to the top. That could be good news for researchers hoping to use engineered “gene drives” to eliminate mosquito-borne diseases and invasive species. But it’s also a cautionary tale for scientists looking for signs that natural selection has picked certain genes because they offer an evolutionary benefit.

If researchers aren’t careful, they may be hoodwinked into thinking that a selfish gene is one that has some evolutionary advantage. The genetic signatures are the same. But what looks like survival of the fittest may actually be a cheater prospering. The selfish DNA could blaze through populations. The proportion of mice with the selfish gene more than tripled in one laboratory population from 18 percent to 62 percent within 13 generations, the researchers found. In another breeding population, R2d2 shot from being in 50 percent of the lab mice to 85 percent in 10 generations. By 15 generations, the selfish element reached “fixation” — all the mice in the population carried it.

Such wildfire spread of a gene variant that eventually wipes out all other versions is known as a selective sweep. Sweeps are hallmarks of a gene that helps an organism adapt to its environment. But this study suggests that what looks like adaptation may actually be selfish genetics at work.

R2d2 is a “selfish element,” a gene or other piece of DNA that causes itself to be inherited preferentially.

The droid’s namesake is a stretch of DNA on mouse chromosome 2 that contains multiple copies of the Cwc22 gene. When seven or more copies of that gene build up on the chromosome, R2d2 gets selfish. In female mice, it elbows aside the chromosome that doesn’t contain the selfish version of the gene and is preferentially incorporated into eggs. That’s a violation of the laws of inheritance spelled out by Gregor Mendel in which each gene or chromosome is supposed to have a fifty-fifty chance of being passed on to the next generation. But there is a cost to R2d2’s selfishness: Female mice that carry one copy of the selfish element have small litter sizes compared with mice that don’t carry the greedy DNA.

Under evolutionary laws, that loss of fertility should cause natural selection to weed outR2d2. But the selfish element’s greed is greater than the power of natural selection to combat it, the lab experiments show.

 The relatively low proportion of wild mice carrying R2d2 could mean that some mice have developed ways to suppress the gene’s selfishness.

- Sciencenews.org


So when people ask me why so many contradictions are emerging in the world of science confusing them, I want to give this reply :

Just studies are different from thorough scientific research. In  studies, I have noted, speculation, beliefs and the opinion of the author plays a major role in coming to a conclusion. Of course the authors can use some examples which look like 'science' but they are faulty in nature. While scientific research and conclusions need proof beyond doubt. Some of  of the study papers are based on  'just studies’ rather than ‘scientific research’ and therefore need not be true and sometimes can be very contradictory to one another.

And meta analyses are not actual scientific research and they are usually done by non-experts in the field and the results could be interpreted in any way. One - especially the media has to be cautious while accepting them and reporting them.

Moreover, different set of conditions in which research is conducted give different results. 

Sometimes, old facts have to be rewritten in the light of new and emerging data.  

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I didn't notice this difference till now!

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