In the human genome, which according to current estimates has about 21, genes [ 15 ] in total, there are about 4, non-coding RNA genes, which include tRNA genes. Cytoplasmic tRNA genes can be grouped into 49 families according to their anticodon features. These genes are found on all chromosomes, except 22 and Y chromosome. High clustering on 6p is observed tRNA genes , as well on 1 chromosome.
Genomic tRNA content is a differentiating feature of genomes among bilogical kingdoms. Archaeas present the most simple situation in terms of genomic tRNA content with a uniform number of gene copy number. Furthermore, Archaeas present little variation in gene copy number among different isoaceptors. Bacteria have an intermediate situation and Eukarya present the most complex situation. Eukarya not only present more tRNA gene content than the other two kingdoms but also present a high variation in gene copy number among different isoacceptors.
This complexity increment along evolution seem to be due to duplications of tRNA genes and changes in anticodon specificity. The anticodon specificity is kingdom-specific and enzymes that post transcriptionally modify the wobble position have an important role in this anticodon specificity among kingdoms. Archeas have no post transcriptionally anticodon modifications in contrast with Bacteria and Eukarya.
This is also related to the codon usage. So, in all kingdoms of life the codon usage is related to translational efficiency because the codon usage is correlated with the gene copy number of different isoaceptors having into account post transcriptionally anticodon modifications.
The transcription terminates after a stretch of four or more thymidines. Pre-tRNAs undergo extensive modifications inside the nucleus. Some pre-tRNAs contain introns that are spliced, or cut, to form the functional tRNA molecule; [ 21 ] in bacteria these self-splice, whereas in eukaryotes and archaea they are removed by tRNA splicing endonuclease.
For example in yeast, the splicing is not carried out in the nucleus but at the cytoplasmic side of mitochondrial membranes. The existence of tRNA was first hypothesized by Francis Crick, based on the assumption that there must exist an adapter molecule capable of mediating the translation of the RNA alphabet into the protein alphabet.
Holley of Cornell University reported the primary structure and suggested three secondary structures. Two independent groups, Kim Sung-Hou working under Alexander Rich and a British group headed by Aaron Klug, published the same crystallography findings within a year. Chat WhatsApp. PMID Nucleic Acids Res. September Bibcode : PNAS PMC Molecular Biology of the Cell. Bibcode : Sci WormBook : the online review of C. Genetics: From Genes to Genomes 2nd ed.
Cell , Trends Genet. Retrieved on 19 July Protein Pept. Bibcode : Natur. Clark October Subscriber sign in You could not be signed in, please check and try again. Username Please enter your Username. Password Please enter your Password. Forgot password?
Don't have an account? Sign in via your Institution. You could not be signed in, please check and try again. Sign in with your library card Please enter your library card number. Reference entries transfer RNA n. Press ESC to cancel.
Ben Davis May 31, What does tRNA bind with? Does tRNA bind to a codon? Which amino acid will be on the tRNA that is the first to bind to the A site of the ribosome?
What does tRNA look like? What is the secondary structure of tRNA? Who gave the structure of tRNA? How stable is tRNA? What degrades tRNA?
0コメント