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Genetics and exercise: an introduction
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Claude Bouchard, Henning Wackerhage
Each mitochondrion of a body (somatic) cell contains several copies of circular, double-stranded DNA molecules composed of 16,569 base pairs. The mitochondrial genome is very small compared to nuclear DNA. Mitochondrial DNA (mtDNA) was successfully sequenced in 1981 (19). mtDNA is able to replicate itself independently of nuclear DNA and has its own system of transcription and translation. The bulk of mtDNA is inherited from the mother through the egg cytoplasm at fertilization, but there is also evidence for paternal inheritance of a few copies of mtDNA. mtDNA codes for 37 RNA transcripts, 28 on the cytosine-rich light strand and 9 on the guanine-rich heavy strand. These 37 RNAs are processed into 13 polypeptides associated with the regeneration of ATP in the mitochondrion, two ribosomal RNAs and 22 transfer RNAs.
Mitochondrial Dysfunction and Hearing Loss
Published in Shamim I. Ahmad, Handbook of Mitochondrial Dysfunction, 2019
There are other mitochondrial mutations, with similar phenotype, the MT-TS1 7476insC, and 7445A-G, which changes the stop codon AGA of the heavy-strand-encoded mRNA for subunit COI of cytochrome c oxidase to an equivalent AGG stop codon and changes a U to C transition in the-light strand-encoded tRNA-ser precursor.17 In these cases, the HL can be the only feature, but it can be accompanied by neurological features.2
The importance of genome sequencing: unraveling SSBP1 variant missed by exome sequencing
Published in Ophthalmic Genetics, 2023
Jae Won Jun, Yuri Seo, Sueng-Han Han, Jinu Han
Visual acuity in SSBP1-related DOA is highly variable, ranging from 20/4000 to 20/20, and even asymptomatic. (5) However, it is generally lower than OPA1-related DOA. In our study, two affected members had a visual acuity of 20/500, which was consistent with SSBP1-related DOA. The reason for SSBP1’s selective damage to the optic nerve and RGCs remains unclear. Since there is a high expression of SSBP1 in early RGC development and low transcription levels in mature retinas, Zelinger et al. proposed the hypothesis that SSBP1 plays a crucial role in mitochondrial biogenesis during early RGC differentiation. They also observed unstable binding to N6-methyldeoxyadenosine on the heavy strand involved in mtDNA replication, leading to optic nerve dysfunction. (15)
Role of Mitochondrial DNA (mtDNA) Variations in Cancer Development: A Systematic Review
Published in Cancer Investigation, 2020
Nisha Thakur, Amitesh Kumar Sharma, Harpreet Singh, Shalini Singh
The mitochondrial chromosome is a closed circular, ds-DNA molecule. The human mtgenome is 1.8 × 10−5 times smaller than the nuclear genome having size of 16,569 bp.The major part of the human mtgenome encrypts 13 protein subunits of the electron transport chain (ETC), two rRNA and twenty twot RNAs genes. The discplacement loop (D-Loop) region is mainly noncoding part of the mtDNA. The maximum transcription of mtDNA takes place in the heavy strand (guanines ‘G’ rich). Though, light strand (cytosine ‘C’ rich) and encodes for eight tRNA and only one protein coding gene. Interestingly, bulk of the mt proteins are encoded by the ncDNA genome and transferred to the mitochondria. Mitochondria are inherited maternally and majority of the cells contain identical copies of mtDNA. Any modification in the mtDNA sequence due to error in the replication and repair mechanism results in disease phenotype and can be of clinical importance (3,4).
The causative variants of amyloidosis in the autism
Published in International Journal of Neuroscience, 2019
Mansoureh Akouchekian, Mitra Hakim Shooshtari, Hamed Heidary, Fateme Zahedi Abghari, Parisa Moeinian
The mitochondrial genome has a total of 37 genes, 22 of them encode transfer RNAs (tRNAs), 2 genes encode ribosomal RNAs (rRNAs) and the remaining 13 genes encode subunits of complexes I and III–V of the electron transferring complex (ETC). These 13 critical genes are, respectively, involved in five complexes of ETC [7]. One of the mitochondrial complexes is cytochrome-c-oxidase (COX). COX is the terminal electron acceptor of the mitochondrial respiratory chain and catalyses the transfer of electrons from reduced cytochrome c to molecular oxygen to form water. COX deficiency is the most commonly recognized respiratory-chain defect in childhood [8]. Mitochondrial genome also consists of a non-coding sequence which is a 1121-bp region called d-loop [9]. Many common mutations have been diagnosed in the mtDNA and most of them accumulate in the regulatory region or d-loop. This region is like a promoter for both light strands (L-strand, Cytosine-rich) and heavy strand (H-strand, Guanine-rich) of mtDNA [10]. Figure 1 shows a simple map of human mitochondrial DNA gene.