Mouse Finding Violates Laws of Heredity (ZT)

liver411

DNA has long been considered the sole arbiter of heredity. New research seems to show, however, that its lesser known cousin, RNA--previously thought only to facilitate the creation of proteins as dictated by the genetic code--may itself pass traits down through the generations.
Fifty years ago, researchers observed that the factors controlling the amount of purple coloring in certain corn kernels deviated from the accepted laws of genetics. Genetic variants that should have been bred out could sometimes exert their empurpling effect in subsequent generations. Dubbed paramutation, the phenomenon remained unexplained.

In experiments with mutant mice, Minoo Rassoulzadegan of Inserm in France and his colleagues observed a similar phenomenon. A mutation in the Kit gene is known to produce white patches of fur on the toes and tails of brown mice. The researchers bred together mice that each carried one normal copy of the gene and one aberrant copy--that is, they were heterozygous. Mice that inherit two normal copies of the gene should not exhibit this coloring. But oddly enough, the team found that a large percentage of the resulting mice in their study that inherited only normal copies of the gene from their heterozygous parents did in fact have the white spots.
Searching for an explanation, the scientists found that the mutant mice bore unusually low levels of regular RNA interspersed with unusually large versions of the messenger molecule. Further, they noticed that this RNA found its way into mouse sperm. And when they injected the RNA into developing embryos it produced the telltale patches in nearly 50 percent of the offspring, who in turn passed the trait along to their offspring. Control mice occasionally exhibited white spots as well, though they rarely passed the trait to subsequent generations.
The exact mechanism by which RNA transmits the spotting trait to progeny in the absence of the gene that causes spotting in the parent remains mysterious. But the finding does challenge the existing understanding of genetics, and it may have implications for humans. In a commentary accompanying the report, Paul Soloway of Cornell University remarks: "A particularly intriguing possibility is that such RNAs regulate other non-genetic modes of inheritance, such as metabolic or behavioral imprinting." The research and commentary appear in today's Nature. --David Biello

http://www.scientificamerican.com/article.cfm?chanID=sa003&articleID=0002F1FB-D535-1474-953583414B7F0000

liver411

“老鼠RNA打破遗传基因定律” zt

Not a good translation but in case someone prefer reading Qin language.
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科学家说，动物能够打破遗传基因定律，将一些遗传特征传给后代。

研究人员发现，老鼠能够将一些特征遗传给后代，尽管这些特征背后欠缺应有的遗传基因。

科学家认为，核糖核酸（RNA，即Ribonucleic Acid)能够将一些特征遗传给后代。

不过，科研人员还要进行更多的实验和研究。

研究人员把一个被称为"Kit"的基因分成"正常"和"变异"两类，被研究的老鼠从父亲遗传了两个"Kit"基因，其中一个变异的" Kit"基因传给他们一条有斑点的尾巴和白色的脚等特征。

根据遗传基因定律，老鼠遗传了正常和变异的"Kit"基因组合，但只有其中一个基因能够决定它是否有一条有斑点的尾巴。

不过科学人员发现，遗传了两个正常"Kit"基因的老鼠也有一条有斑点的"附属肢体"（尾巴）。

他们认为，核糖核酸（RNA）分子将这一特征遗传给后代。核糖核酸是一种多聚核苷酸，和脱氧核糖核酸（DNA）一样，在身体的合成蛋白质和其他化学活动中担当重要的角色。

近年来，科学家们搜集了许多间接性的证据，表明由脱氧核糖核酸（DNA）分子构成的基因传递，不是影响遗传的唯一因素。

BBC科技事务记者莫雷尔报道

medline

Egg comes from hen, hen comes from little hen, little hen comes from egg.
Hen and egg. which one comes first?

Back to long long time ago, where there was only one cell organism.In that case, hen and egg become one identical cell.  So we don't need to worry about which one comes the first, because they are the same thing.

DNA, RNA , protein. Protein comes from RNA, RNA comes from DNA, DNA needs protein in order to replicate  itself or synthesis RNA. So, the question is , DNA and protein, which comes first?

Now, people have found that in some case, RNA can play the role as both DNA and protein.
RNA can act as DNA to become replicating templete and to duplicate itself.
RNA can also act as protein to catalyze reclicating actions, which previously people think only enzyme (which is protein) can do. This kind of enzyme like RNA are called Ribozyme.

So the question for DNA and protein seems a little easy, they might both comes from RNA when it's long long time ago.

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RNA is very interesting. The top post given a new story that RNA might also be able to  play a role of heredity even in mouse, which is one highly evolved mammalian species. Nature is incredible.

[此贴子已经被作者于2006-5-29 6:07:17编辑过]