Note4Students
From UPSC perspective, the following things are important :
Prelims level: Mitochondria, mtDNA
Why in the News?
Recent research indicates that age-related losses in our cell’s mitochondrial DNA (mtDNA)—specifically, deletion mutations—could be a major driver of aging. These mutations, once they accumulate, reduce the mitochondrion’s ability to produce energy (ATP), causing cell and tissue dysfunction.
What are Mitochondria?
- Mitochondria generate most of the cell’s energy (hence called the Powerhouse) in the form of ATP (adenosine triphosphate).
- They originated from free-living bacteria absorbed by ancient single-celled organisms, retaining a fraction of their own DNA (mtDNA).
- Unlike nuclear DNA, mitochondria have their own circular DNA, though limited in size.
- Humans inherit mitochondria exclusively from the mother’s egg; sperm-contributed mitochondria are generally not passed on.
- They have a double membrane: a relatively permeable outer membrane and a highly folded inner membrane (cristae) that maximizes surface area for energy production.
- Their inner compartment, the mitochondrial matrix, houses mitochondrial DNA (mtDNA), ribosomes, and enzymes for the Krebs cycle (citric acid cycle) and fatty acid β-oxidation.
- Mitochondria help regulate intracellular calcium levels, which is crucial for various signalling pathways.
- They play a role in apoptosis (programmed cell death) by releasing factors such as cytochrome c when the cell is under severe stress.
Functions of DNA, mRNA, and the gene:
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Functions of the Mitochondrial Genome (mtDNA):
- Encodes Key Mitochondrial Proteins:
- The mtDNA has 13 protein-coding genes crucial for mitochondrial energy production (ATP synthesis).
- It also encodes 24 non-coding genes (like rRNAs and tRNAs), essential for mitochondrial protein synthesis.
- Energy Production:
- mtDNA-encoded proteins form part of the electron transport chain, where most ATP is produced.
- Distinct Inheritance Pattern:
- Inherited exclusively from the mother.
- Each cell contains multiple mitochondria, each with multiple copies of mtDNA.
- Implication in Aging and Disease:
- Age-related mutations (deletions, chimeric genes) in mtDNA can lead to functional decline in tissues like muscle and brain.
- Loss of intact mtDNA reduces ATP generation, contributing to cellular and tissue ageing.
PYQ:[2021] In the context of hereditary diseases, consider the following statements:
Which of the statements given above is/are correct? (a) 1 only |
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