 |
Business | Industries | Finance | Tax |
| Index: > A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
|
|||||
| First Prev [ 1 2 ] Next Last |
The most prominent examples of non-coding RNAs are transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in the process of translation. However, since the late 1990s, many new non-coding RNAs have been found, and thus non-coding RNAs may play a much more significant role than previously thought. Even so, they are probably not as significant or numerous as the proteins.
Ribosomal RNA (rRNA) is the primary constituent of ribosomes. Ribosomes are the protein-manufacturing organelles of cells and exist in the cytoplasm. rRNA is transcribed from DNA, like all RNA, and in eukaryotes it is processed in the nucleolus before being transported through the nuclear membrane. This type of RNA makes up the vast majority of RNA found in a typical cell (~95%). While proteins are also present in the ribosomes, the 23s rRNA forms the active site for peptide bond formation, making that molecule a ribozyme.
Many non-coding RNAs are structural elements in the untranslated regions of mRNAs (i.e. cis-regulatory RNAs), for example riboswitches and the SECIS elementIn biology, the SECIS element (SECIS: se leno c ysteine i nsertion s equence is a structural motif (pattern of nucleotides) that directs the cell to translate UGA codons as selenocysteines. UGA is normally a stop codon. SECIS elements are thus a fundament.
Small nuclear RNA (snRNA) is a class of small RNA molecules that are found within the nucleus of eukaryotic cells. They are involved in a variety of important processes such as RNA splicing (removal of intronIntrons are sections of DNA within a gene that do not encode part of the protein that the gene produces, and are spliced out of the mRNA that is transcribed from the gene before it is exported from the cell nucleus. Introns exist mainly (but not only) ins from hnRNA) and maintaining the telomereA telomere is a region of highly repetitive DNA at the end of a chromosome, which functions as an aglet. Every time linear eukaryotic chromosomes are replicated, the DNA polymerase complex stops several hundred bases before the end; if it were not for tels. They are always associated with specific proteins, and the complexes are referred to as small nuclear ribonucleoprotein s (snRNP) or sometimes as snurps.
Small nucleolar RNA (snoRNA) is a class of small RNA molecules that are involved in chemical modifications of ribosomal RNAs (rRNAs) and other RNA genes, for example by methylationMethylation is the addition of a methyl group to any substrate. When used in the context of epigenetics, methylation can refer to the addition of a methyl group to a cytosine residue of DNA to convert it to 5-methylcytosine or the addition of a methyl gro. snoRNAs are a component in the small nucleolar ribonucleoprotein (snoRNP), which contains snoRNA and proteins. The snoRNA guides the snoRNP complex to the modification site of the target RNA gene via sequences in the snoRNA that hybridize to the target site. The proteins then catalyze modification of the RNA gene.
microRNA (also miRNA) are RNA genes that are the reverse complement of another gene's mRNA transcript and inhibit the expression of the target gene.
See miRNAIn genetics, a miRNA (micro-RNA) is a form of single-stranded RNA which is typically 20-25 nucleotides long, and is thought to regulate the expression of other genes. miRNAs are RNA genes which are transcribed from DNA, but are not translated into protein.
| Politics | Business | Finance |
 |
 |
 |