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Animal Mitochondrial Genetics

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Among all the organelles in an animal cell, only mitochondria have their own independent genomes. Animal mitochondrial DNA is a double-stranded, closed-circular molecule with around 20,000 base pairs. Mitochondrial DNA is unique in that one of its two strands, the heavy, or H, -strand is guanine rich, whereas the complementary strand is cytosine rich and called the light, or L, -strand. Compared to nuclear DNA, mitochondrial DNA has a very low percentage of non-coding regions and is marked by...

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Related Experiment Video

Updated: Jun 12, 2026

Discrimintion and Mapping of the Primary and Processed Transcripts in Maize Mitochondrion Using a Circular RT-PCR-based Strategy

Discrimintion and Mapping of the Primary and Processed Transcripts in Maize Mitochondrion Using a Circular RT-PCR-based Strategy

Published on: July 29, 2019

Expression of four mitochondrial tRNAs from only two loci.

Jessica M Warren^1,2, Kasavajhala V S K Prasad³, Anistynn M Mendez¹

¹Biodesign Institute and School of Life Sciences, Arizona State University, Tempe, AZ 85281.

Proceedings of the National Academy of Sciences of the United States of America

|June 10, 2026

Summary

Mitochondria use "mirror" transfer RNAs (tRNAs) from a single gene locus to decode two amino acids. This discovery reveals a novel strategy for maintaining essential mitochondrial tRNAs during extensive gene loss.

Keywords:

bidirectional transcription mitochondrial genome evolution mitochondrial tRNAs

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Last Updated: Jun 12, 2026

Discrimintion and Mapping of the Primary and Processed Transcripts in Maize Mitochondrion Using a Circular RT-PCR-based Strategy

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Published on: July 29, 2019

Isolation of mRNAs Associated with Yeast Mitochondria to Study Mechanisms of Localized Translation

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Published on: March 14, 2014

Simultaneous Mapping and Quantitation of Ribonucleotides in Human Mitochondrial DNA

Simultaneous Mapping and Quantitation of Ribonucleotides in Human Mitochondrial DNA

Published on: November 14, 2017

Area of Science:

Mitochondrial biology
Molecular evolution
RNA biology

Background:

Animal mitochondrial genomes retain few genes, including transfer RNAs (tRNAs), from bacterial ancestors.
Mitochondrial tRNAs (mt-tRNAs) are often structurally aberrant and can be truncated, challenging definitions of functional tRNAs.

Purpose of the Study:

To investigate novel tRNA gene architectures in animal mitochondria.
To characterize a unique "mirror" tRNA pair produced from opposite strands of the same locus.

Main Methods:

Analysis of mitochondrial genome architecture.
Biochemical assays to confirm aminoacylation of mirror tRNAs.
Localization studies within mitoribosomes.
Investigation of posttranscriptional modifications and RNA editing.

Main Results:

Identified two overlapping "mirror" tRNAs transcribed from opposite strands of a single locus.
Demonstrated that these mirror tRNAs are aminoacylated and functional within mitoribosomes.
Observed strand-specific nucleotide modifications and RNA editing on mirror tRNAs, dependent on transcriptional orientation.

Conclusions:

Mirror tRNAs represent a novel mechanism for maintaining a complete tRNA set in compact mitochondrial genomes.
This bidirectional gene expression strategy has significant implications for the evolution of tRNA genes, mitochondrial function, and the origins of protein synthesis.