Related Experiment Video
Updated: May 7, 2026

Simultaneous Mapping and Quantitation of Ribonucleotides in Human Mitochondrial DNA
Published on: November 14, 2017
The tRNA genes punctuate the reading of genetic information in human mitochondrial DNA
Abstract:
A detailed transcription map of HeLa cell mitochondrial DNA (mtDNA) has been constructed by using the S1 protection technique to localize precisely the sequences coding for the ribosomal RNA (rRNA) and poly(A)-containing species on the physical map of the DNA. This transcription map has been correlated with the positions of the tRNA genes derived from the mtDNA sequence. It has been shown that, with the exception of the D loop and another small segment near the origin of replication, the mtDNA sequences are completely saturated by the rRNAs, poly(A)-containing RNAs and tRNA coded for by the two strands. No evidence for intervening sequences has been found. The sequences coding for the individual poly(A)-containing RNA and rRNA species appear to be immediately contiguous on one side, and most frequently on both sides, to tRNA coding sequences. Furthermore, the H strand sequences coding for the two rRNAs, the poly(A)-containing RNAs and the tRNAs appear to be adjacent to each other, extending from coordinate 2/100 to coordinate 95/100 of the genome relative to the origin taken as 0/100. The results are consistent with a model of transcription of the H strand in the form of a single molecule which is processed into mature RNA species by precise endonucleolytic cleavages, occurring in almost all cases immediately before and after a tRNA sequence. The tRNA sequences may play an important role as recognition signals in the processing of the primary transcripts.
Related Concept Videos
From DNA to Protein
Animal Mitochondrial Genetics
Export of Mitochondrial and Chloroplast Genes
Transfer RNA Synthesis
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
Mitochondrial Protein Sorting
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...

