Related Experiment Video

Updated: Sep 10, 2026

Measuring Single-Cell Mitochondrial DNA Copy Number and Heteroplasmy Using Digital Droplet Polymerase Chain Reaction
09:15

Measuring Single-Cell Mitochondrial DNA Copy Number and Heteroplasmy Using Digital Droplet Polymerase Chain Reaction

Published on: July 12, 2022

Uneven distribution of mitochondrial DNA mutation in MERRF dizygotic twins

I Penisson-Besnier1, F Degoul, C Desnuelle

  • 1INSERM U. 298, CHRU Angers, France.

Journal of the Neurological Sciences
|July 1, 1992
PubMed

Insights

A novel myoclonic epilepsy with ragged-red fibers (MERRF) family showed varied symptoms and multiple respiratory chain defects. A specific mitochondrial DNA mutation was identified, with twin data suggesting early genome segregation.

Area of Science:

  • Genetics
  • Neurology
  • Mitochondrial Diseases

Background:

  • Myoclonic epilepsy with ragged-red fibers (MERRF) is a maternally inherited mitochondrial disorder.
  • Understanding the genetic basis and clinical variability of MERRF is crucial for diagnosis and management.

Observation:

  • A MERRF family presented with significant variations in age of onset, clinical symptoms, and disease severity.
  • Two patients exhibited multiple defects in respiratory chain complexes I, III, and IV.
  • A consistent point mutation at position 8344 in the mitochondrial genome was found across the maternal lineage.

Findings:

  • The study identified the 8344 mitochondrial DNA (mtDNA) point mutation in all affected maternal relatives.
  • Dizygotic twins displayed discordant phenotypes: one affected with high mutant mtDNA levels, the other asymptomatic with low levels.
  • This discordance in twins suggests potential early segregation of mutant mtDNA during oogenesis.

Implications:

  • The findings highlight the complex genotype-phenotype correlations in MERRF.
  • Early mtDNA segregation may significantly influence disease manifestation and severity.
  • Further research into mitochondrial inheritance patterns can improve understanding of MERRF pathogenesis.

More Related Videos

Genotyping Single Nucleotide Polymorphisms in the Mitochondrial Genome by Pyrosequencing07:24

Genotyping Single Nucleotide Polymorphisms in the Mitochondrial Genome by Pyrosequencing

Published on: February 10, 2023

Transmitochondrial Cybrid Generation Using Cancer Cell Lines07:49

Transmitochondrial Cybrid Generation Using Cancer Cell Lines

Published on: March 17, 2023

Related Concept Videos

Mismatch Repair01:48

Mismatch Repair

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.The Mutator Protein Family Plays a Key Role in DNA Mismatch RepairThe human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
Sex-linked Disorders02:28

Sex-linked Disorders

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.Y chromosome mutations are called “Y-linked” and only affect males since they alone carry a copy of that chromosome. Mutations to the relatively small Y chromosome can impact male sexual function and secondary sex characteristics. Y-chromosome infertility is a disorder that affects sperm...
Nondisjunction02:14

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.When...
Animal Mitochondrial Genetics02:59

Animal Mitochondrial Genetics

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...
Mismatch Repair01:20

Mismatch Repair

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
Nondisjunction01:21

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers.  Nondisjunction is common during anaphase I or anaphase II of meiosis.  Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...