Junk DNA

In molecular biology, "junk" DNA is a provisional label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified. Scientists fully expect to find functions for some, but definitely not all, of this provisionally classified collection. About 80-90% of the human genome has been designated as "junk", including most sequences within introns and most intergenic DNA. While much of this sequence may be an evolutionary artifact that serves no present-day purpose, some is believed to function in ways that are not currently understood. Moreover, the conservation of some junk DNA over many millions of years of evolution may imply an essential function. Some consider the "junk" label as something of a misnomer, but others consider it apposite as junk is stored away for possible new uses, rather than thrown out; others prefer the term "noncoding DNA" (although junk DNA often includes transposons that encode proteins with no clear value to their host genome). However it now appears that, although protein-coding DNA makes up barely 2% of the human genome, about 80% of the bases in the genome may be transcribed, ^[1]but transcription by itself does not necessarily imply function.

Broadly, the science of functional genomics has developed widely accepted techniques to characterize protein-coding genes, RNA genes, and regulatory regions. In the genomes of most plants and animals, however, these together constitute only a small percentage of genomic DNA (less than 2% in the case of humans). The function, if any, of the remainder remains under investigation. Most of it can be identified as repetitive elements that have no known biological function for their host (although they are useful to geneticists for analyzing lineage and phylogeny). Still, a large amount of sequence in these genomes falls under no existing classification other than "junk".

Overall genome size, and by extension the amount of junk DNA, appears to have little relationship to organism complexity: the genome of the unicellular Amoeba dubia has been reported to contain more than 200 times the amount of DNA in humans"^{[2] [3]}.

The pufferfish Takifugu rubripes genome is only about one tenth the size of the human genome, yet seems to have a comparable number of genes. Most of the difference appears to lie in what is now known only as junk DNA. This puzzle is known as the C-value enigma or, more conventionally, the C-value paradox

http://en.wikipedia.org/wiki/Junk_DNA

Dow Jones Industrial Index Hanging Man Candlestick Charting Pattern Invalidated

With the latest strong candlestick formation the hanging man candlestick chart pattern formed earlier has lost its bearish power. Expect closing above black downtrend line today. Trading will probably still be restricted within the blue raising wedge lines. If the unexpected happens a drop towards mid Bolinger Band support at 12575 will be imminent.

Cosco 15 mins chart testing intraday low

Testing of intraday low at $3.41 is imminent. Any retracement will meet resistance at the green downtrend line, 20 EMA and 50 EMA resistance lines. Breakdown below intraday low will retest 200 EMA support and gap support at $3.34

RNA Structure

Each nucleotide in RNA contains a ribose sugar, with carbons numbered 1' through 5'. A base is attached to the 1' position, generally adenine (A), cytosine (C), guanine (G) or uracil (U). Adenine and guanine are purines, cytosine and uracil are pyrimidines. A phosphate group is attached to the 3' position of one ribose and the 5' position of the next. The phosphate groups have a negative charge each at physiological pH, making RNA a charged molecule (polyanion). The bases may form hydrogen bonds between cytosine and guanine, between adenine and uracil and between guanine and uracil.^[1] However other interactions are possible, such as a group of adenine bases binding to each other in a bulge,^[2] or the GNRA tetraloop that has a guanine–adenine base-pair.^[1]

Chemical structure of RNA

An important structural feature of RNA that distinguishes it from DNA is the presence of a hydroxyl group at the 2' position of the ribose sugar. The presence of this functional group causes the helix to adopt the A-form geometry rather than the B-form most commonly observed in DNA.^[3] This results in a very deep and narrow major groove and a shallow and wide minor groove.^[4] A second consequence of the presence of the 2'-hydroxyl group is that in conformationally flexible regions of an RNA molecule (that is, not involved in formation of a double helix), it can chemically attack the adjacent phosphodiester bond to cleave the backbone.^[5]

RNA is transcribed with only four bases (adenine, cytosine, guanine and uracil),^[6] but there are numerous modified bases and sugars in mature RNAs. Pseudouridine (Ψ), in which the linkage between uracil and ribose is changed from a C–N bond to a C–C bond, and ribothymidine (T), are found in various places (most notably in the TΨC loop of tRNA).^[7] Another notable modified base is hypoxanthine, a deaminated adenine base whose nucleoside is called inosine. Inosine plays a key role in the wobble hypothesis of the genetic code.^[8] There are nearly 100 other naturally occurring modified nucleosides,^[9] of which pseudouridine and nucleosides with 2'-O-methylribose are the most common.^[10] The specific roles of many of these modifications in RNA are not fully understood. However, it is notable that in ribosomal RNA, many of the post-transcriptional modifications occur in highly functional regions, such as the peptidyl transferase center and the subunit interface, implying that they are important for normal function.^[11]

Secondary structure of a telomerase RNA

The functional form of single stranded RNA molecules, just like proteins, frequently requires a specific tertiary structure. The scaffold for this structure is provided by secondary structural elements which are hydrogen bonds within the molecule. This leads to several recognizable "domains" of secondary structure like hairpin loops, bulges and internal loops.^[12] There has been a significant amount of research directed at the RNA structure prediction problem.

Watson-Crick base pairs in a siRNA (hydrogen atoms are not shown)

http://en.wikipedia.org/wiki/RNA

What are the similarities and differences between embryonic and adult stem cells?

Human embryonic and adult stem cells each have advantages and disadvantages regarding potential use for cell-based regenerative therapies. Of course, adult and embryonic stem cells differ in the number and type of differentiated cells types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are generally limited to differentiating into different cell types of their tissue of origin. However, some evidence suggests that adult stem cell plasticity may exist, increasing the number of cell types a given adult stem cell can become.

Large numbers of embryonic stem cells can be relatively easily grown in culture, while adult stem cells are rare in mature tissues and methods for expanding their numbers in cell culture have not yet been worked out. This is an important distinction, as large numbers of cells are needed for stem cell replacement therapies.

A potential advantage of using stem cells from an adult is that the patient's own cells could be expanded in culture and then reintroduced into the patient. The use of the patient's own adult stem cells would mean that the cells would not be rejected by the immune system. This represents a significant advantage as immune rejection is a difficult problem that can only be circumvented with immunosuppressive drugs.

Embryonic stem cells from a donor introduced into a patient could cause transplant rejection. However, whether the recipient would reject donor embryonic stem cells has not been determined in human experiments.

http://stemcells.nih.gov/info/basics/basics5.asp