IAS Gyan

Daily News Analysis


10th July, 2024 Health


Source: BusinessStandard

Disclaimer: Copyright infringement not intended.


  • Scientists are currently preparing for a clinical trial to determine whether mitochondrial donation is safe and effective, following the passage of a law in Australia in 2022 that will allow for the practice.


Mitochondrial Donation

  • An IVF-based procedure that prevents the transmission of faulty mitochondrial DNA, allowing families to have healthy, genetically related children.
  • Process:
    • Hormone Injections: Stimulate egg production in both the donor and the affected individual.
    • Egg Retrieval: Collect eggs from both the donor and the affected individual using an ultrasound-guided procedure.
    • Nuclear DNA Transfer: Extract the nuclear DNA from the affected individual’s egg and insert it into the donor egg with healthy mitochondria.
    • Fertilization: Use sperm from the intending father to fertilize the modified donor egg​​.

Legal and Ethical Considerations

  • Maeve's Law: The Mitochondrial Donation Law Reform Bill 2021, passed by the Australian Senate in 2022, allows mitochondrial donation for research and clinical trials under strict regulations.
  • Requirements:
    • Facilities must obtain special permits.
    • Initial licenses for pre-clinical and clinical trial research to ensure safety and effectiveness​​.

What is Mitochondrial Disease?

  • Mitochondrial diseases are a group of disorders caused by dysfunctional mitochondria, the organelles that generate energy for the cell.
  • These diseases can affect multiple organs and systems, including the brain, heart, liver, muscles, kidneys, and endocrine system.
  • Affects 1 in every 5,000 people, making it a common inherited metabolic condition.


  • Mitochondrial diseases are primarily genetic, resulting from mutations in either nuclear DNA (nDNA) or mitochondrial DNA (mtDNA).
  • They can be inherited in several ways:
  • Autosomal Recessive/Dominant Inheritance: Mutations in nDNA inherited from both or one parent.
  • Mitochondrial Inheritance: Mutations in mtDNA passed down from the mother.
  • De Novo Mutations: New mutations that occur spontaneously without a family history​​.


Symptoms of mitochondrial diseases vary widely and can include:

  • Muscle weakness and exercise intolerance
  • Neurological issues such as seizures, migraines, and developmental delays
  • Cardiomyopathy and other heart issues
  • Liver and kidney dysfunction
  • Endocrine problems, including diabetes and growth delays
  • Gastrointestinal disturbances
  • Visual and hearing impairments​​.

Types of Mitochondrial Diseases

There are several types of mitochondrial diseases, each with unique characteristics. Some notable types include:

  • Leigh Syndrome: Severe neurological disorder
  • MELAS (Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes)
  • MERRF (Myoclonic Epilepsy with Ragged Red Fibers)
  • Kearns-Sayre Syndrome
  • Barth Syndrome
  • Alpers Disease
  • Chronic Progressive External Ophthalmoplegia (CPEO)
  • Friedreich's Ataxia​


  • Mitochondria are double-membrane-bound organelles found in the cytoplasm of almost all eukaryotic cells.
  • They are often referred to as the "powerhouses" of the cell because they generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

Structure of Mitochondria

  • Outer Membrane
    • Smooth and permeable to small molecules and ions.
    • Contains proteins called porins that allow molecules to pass through.
    • Involved in various functions such as lipid metabolism and the maintenance of mitochondrial shape.
  • Intermembrane Space
    • The area between the inner and outer membranes.
    • Contains enzymes that use the ATP moving out of the matrix to phosphorylate other nucleotides.
    • Plays a role in apoptosis (programmed cell death).
  • Inner Membrane
    • Folded into structures called cristae to increase surface area.
    • Contains proteins involved in the electron transport chain and ATP synthesis.
    • Impermeable to most ions and molecules; transport is highly regulated.
  • Matrix
    • Enclosed by the inner membrane.
    • Contains mitochondrial DNA (mtDNA), ribosomes, and enzymes involved in the citric acid cycle (Krebs cycle) and fatty acid oxidation.
    • The site of ATP production through oxidative phosphorylation.

Functions of Mitochondria

  • Energy Production
    • Primary site of ATP production via oxidative phosphorylation.
    • Citric acid cycle (Krebs cycle) takes place in the matrix, generating high-energy electron carriers.
  • Regulation of Metabolic Activity
    • Involved in various metabolic tasks including the synthesis of certain steroids and heme.
    • Plays a role in the regulation of cellular metabolism.
  • Apoptosis: Mitochondria release cytochrome c, triggering the cascade of events leading to programmed cell death.
  • Calcium Storage: Store calcium ions and help maintain cellular calcium homeostasis.
  • Heat Production: In brown adipose tissue, mitochondria generate heat through a process called non-shivering thermogenesis.
  • ROS Production: By-products of the electron transport chain include reactive oxygen species (ROS), which play roles in cell signaling and homeostasis.

Mitochondrial DNA

  • mtDNAis circular and maternally inherited.
  • Encodes 37 genes, including 13 for proteins, 22 for tRNA, and 2 for rRNA.
  • Mutations in mtDNA can lead to various mitochondrial diseases.

Biogenesis and Dynamics


  • Mitochondrial biogenesis is the process by which new mitochondria are formed in the cell.
  • Regulated by several factors including PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha).


  • Mitochondria constantly undergo fusion (joining) and fission (splitting).
  • Fusion helps mitigate stress by mixing the contents of partially damaged mitochondria as a form of complementation.
  • Fission helps create new mitochondria and is important for cellular distribution and apoptosis.

 Summary of all major cell organelles







Double membrane with pores; contains nucleolus and chromatin

Stores genetic material (DNA); controls cellular activities; site of transcription

Eukaryotic cells


Double membrane; inner membrane folded into cristae

ATP production through oxidative phosphorylation; regulates cellular metabolism

Eukaryotic cells


Composed of rRNA and proteins; can be free or bound

Protein synthesis

All cells

Endoplasmic Reticulum (ER)

Network of membranous tubules; rough ER has ribosomes, smooth ER does not

Rough ER: Protein synthesis and processing; Smooth ER: Lipid synthesis and detoxification

Eukaryotic cells

Golgi Apparatus

Stacks of flattened membranous sacs

Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles

Eukaryotic cells


Membrane-bound vesicles containing hydrolytic enzymes

Breakdown of macromolecules; recycling of cellular components; apoptosis

Animal cells primarily


Membrane-bound vesicles containing oxidative enzymes

Breakdown of fatty acids; detoxification of harmful substances

Eukaryotic cells


Double membrane with internal thylakoid stacks

Photosynthesis; conversion of light energy into chemical energy (glucose)

Plant cells and algae


Membrane-bound sacs; large central vacuole in plant cells

Storage of nutrients and waste products; maintenance of turgor pressure in plant cells

Eukaryotic cells

Cell Membrane

Phospholipid bilayer with embedded proteins

Selective barrier; regulates transport of substances in and out of the cell

All cells

Cell Wall

Rigid structure outside the cell membrane; composed of cellulose in plants

Provides structural support and protection

Plant cells, fungi, some prokaryotes


Network of protein fibers (microfilaments, intermediate filaments, microtubules)

Maintains cell shape; facilitates cell movement and division; transports materials within the cell

Eukaryotic cells


Cylindrical structures composed of microtubules

Involved in cell division; organizes the mitotic spindle

Animal cells primarily


Dense region within the nucleus

Ribosome biogenesis

Eukaryotic cells


Gel-like substance within the cell membrane

Holds organelles; site of many metabolic pathways

All cells


Double membrane; includes chloroplasts, chromoplasts, and leucoplasts

Involved in synthesis and storage of food

Plant cells

Cilia and Flagella

Hair-like structures on cell surface

Movement of the cell or movement of fluids over the cell surface

Some eukaryotic cells




Q: Consider the following statements regarding Mitochondrial DNA (mtDNA):

  1. Mitochondrial DNA is circular and contains 37 genes essential for mitochondrial function.
  2. Unlike nuclear DNA, mitochondrial DNA is inherited exclusively from the mother.
  3. Mitochondrial DNA has a higher mutation rate compared to nuclear DNA due to its proximity to the electron transport chain and lack of protective histones.

Which of the statements given above is/are correct?

a) 1 and 2 only
b) 2 and 3 only
c) 1 and 3 only
d) 1, 2, and 3

Answer: d)