Genetics · MU Sofia

3. Organization of the mitochondrial genome.

Explains the human mitochondrial genome: its small circular structure, high copy number and lack of introns, then the 37 genes it carries, split into protein-coding, tRNA and rRNA groups. Covers replication by the D-loop mechanism, polycistronic transcription, and the altered genetic code, followed by maternal inheritance, heteroplasmy, the threshold effect and high mutation rate. Ends with clinical disorders such as LHON, MELAS, MERRF and Leigh syndrome, plus ageing and forensic uses.

Inside: 8 sections · 5 labelled pictures · 16 flashcards · 5 min

Topic 3 of 65 in the MU Sofia syllabus for Genetics (Medicine, Year 3). The free AceMed note covers it in 8 sections, about 706 words (5 min of reading), with 16 flashcards.

In this note

  1. Topic 3 – Organization of the Mitochondrial Genome
  2. I. Introduction
  3. II. General Features of the Human Mitochondrial Genome
  4. III. Gene Content
  5. IV. Replication and Transcription
  6. V. Inheritance and Mutation
  7. VI. Clinical Relevance
  8. VII. Key Points

I. Introduction

Mitochondria are known as the powerhouses of the cell because they generate most of the ATP through oxidative phosphorylation.

2Unlike other organelles, they are semi-autonomous: they contain their own DNA, transcription, and translation machinery. This makes them similar to bacteria, supporting the endosymbiotic theory (mitochondria originated from prokaryotes that entered ancestral eukaryotic cells).

The mitochondrial genome is much smaller than the nuclear genome, but it is essential for energy metabolism. Without it, cells cannot sustain high energy-demanding processes like muscle contraction or neuronal signaling.

II. General Features of the Human Mitochondrial Genome

  • Shape and size: A closed circular double-stranded DNA molecule, about 16,569 base pairs in humans. This is tiny compared to the nuclear genome (~3.2 billion base pairs).
  • Copy number: Each mitochondrion contains several copies of mtDNA, and a typical cell may have hundreds to thousands of mitochondria, giving a very high total copy number of mtDNA per cell. This high redundancy is important for function and resilience.
  • No introns: Unlike nuclear DNA, mtDNA is extremely compact. Almost every base is part of a gene or a control sequence. This means no “junk DNA” and no introns interrupting genes.

Continue reading free

The whole note, all 8 sections, is free with an AceMed account, with its 16 flashcards. Premium adds flashcard recall, highlights and Ask AI.

Start freeAlready a member? Open the note