There are too many kinds of RNA not to peak your curiosity. Why does it occur in such a wide variety of forms? Ribo Nucleic Acid
There is more to this molecule that can replicate itself, than the three simple letters might suggest.
There are too many kinds of RNA not to peak your curiosity. Why does it occur in such a wide variety of forms?
Once thought to translate the base pair sequences of DNA, shown here on below, as the "Genetic Code," RNA turns out to be a master builder of organelles or tiny bodies within larger cells as well as the cells themselves.
RNA acts as a "go between," an arranger, and an editor among other things, as it behaves in such a manner as to greatly influence the governing of cellular behavior.
| RNA is Coded for in the Genome | Chromosomes comprise the Genome |
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| Ribose a sugar is the marker for RNARNA | RNA interprets the DNA to build proteins |
RNA is a versatile molecule. In its most familiar role, RNA acts as an intermediary, carrying genetic information from the DNA to the machinery of protein synthesis. RNA also plays more active roles, performing many of the catalytic and recognition functions normally reserved for proteins. In fact, most of the RNA in cells is found in ribosomes--our protein-synthesizing machines--and the transfer RNA molecules used to add each new amino acid to growing proteins. In addition, countless small RNA molecules are involved in regulating, processing and disposing of the constant traffic of messenger RNA. The enzyme RNA polymerase carries the weighty responsibility of creating all of these different RNA molecules. Ribonucleic Acid the molecule that acts as an enzyme and automatically replicates Messenger RNA mRNA
mRNA shape is not important the sequence of base pairs is Double stranded RNA related to RNAi (RNA interference
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Transfer RNA or tRNA
tRNA is a small 76 base long molecule folded into peculiar shapes.
Each tRNA relates has a specific amino acid sequence attached to it and recognizes a particular amino acid codon sequence of three base pairs of a mRTNA. tRNA acts to transfer a base pair sequence of mRNA into an Amino Acid sequence.
Ribozymes as many as 1,500 varieties in the five kingdoms, several hundred nucleotides long.
Hammerhead ribozymes – 40 sequences long are the smallest RNA molecule –as yet—found, usually in viruses that infect plants. It cuts DNA sequences
Hepatitis Delta Virus cleaves DNA is about 90 nucleotides long (HDV)
Ribonuclease P, a ribonucleoprotein that is 90 nucleotides long
A Ribosome is actually three ribonucleoproteins that synthesize proteins.
“RNA does a lot of different things” based on its single stranded structure, variable length and structure or shape.
RNA probably predates DNA. Moves about where DNA remains hidden in nucleosomes of eukaryotic organisms.
http://www.hhmi.org/biointeractive/rna/rnadiversity/index.html, 11-16-05 9:23PM
RNA interference or RNAi
RNAi turns off certain gene expression, halting the replication of proteins by ribosomes.
RNA interference and translational control
RNA interference (RNAi) represents an evolutionary conserved cellular defense mechanism for controlling the expression of alien genes in filamentous fungi, plants, and animals. It is caused by sequence-specific mRNA degradation, and is mediated by double-stranded RNA (dsRNA) homologous in sequence to the target RNA. dsRNA is often a byproduct of viral replication or is formed by aberrant transcription from genetic elements after random integration in the host genome.
RNA polymerase
The RNA Factory
RNA polymerase is a huge factory with many moving parts. The one shown here, from PDB entry 1i6h, is from yeast cells. It is composed of a dozen different proteins. Together, they form a machine that surrounds DNA strands, unwinds them, and builds an RNA strand based on the information held inside the DNA. Once the enzyme gets started, RNA polymerase marches confidently along the DNA copying RNA strands thousands of nucleotides long.
Accuracy
As you might expect, RNA polymerase needs to be accurate in its copying of genetic information. To improve its accuracy, it performs a simple proofreading step as it builds an RNA strand. The active site is designed to be able to remove nucleotides as well as add them to the growing strand. The enzyme tends to hover around mismatched nucleotides longer than properly added ones, giving the enzyme time to remove them. This process is somewhat wasteful, since proper nucleotides are also occasionally removed, but this is a small price to pay for creating better RNA transcripts.
Overall, RNA polymerase makes an error about once in 10,000 nucleotides added, or about once per RNA strand created.
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