Q.70 Analysis of DNA sequences suggest that eukaryotic mitochondrial genomes primarily
originated from
(A) fungi (B) protozoa (C) algae (D) bacteria
Eukaryotic mitochondrial genomes originated primarily from bacteria, as confirmed by DNA sequence analysis supporting the endosymbiotic theory.
This CSIR NET-style question tests knowledge of organelle evolution in molecular biology.
Correct Answer
(D) bacteria
Phylogenetic analyses of mitochondrial DNA (mtDNA) show close relatedness to alpha-proteobacteria, an alphaproteobacterial group. Circular mtDNA structure, bacterial-like ribosomes, and gene content further match prokaryotic genomes, not eukaryotic ones from fungi, protozoa, or algae.
Option Analysis
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(A) Fungi: Fungal mitochondria derive from the same bacterial ancestor; their nuclear genomes show opisthokont relations to animals, but mtDNA remains bacterial.
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(B) Protozoa: Protozoan mtDNA varies but traces to bacteria; no evidence supports protozoa as mitochondrial source.
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(B) Protozoa: Protozoan mtDNA varies but traces to bacteria; no evidence supports protozoa as mitochondrial source.
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(C) Algae: Algal mitochondria follow bacterial origin; chloroplasts come from cyanobacteria, but mitochondria do not.
Eukaryotic mitochondrial genomes originated from bacteria, a key fact backed by DNA sequence analysis in evolutionary biology. This endosymbiotic origin explains mtDNA’s bacterial features in eukaryotic cells.
Endosymbiotic Theory Basics
Mitochondria arose when an ancestral eukaryotic host engulfed an alpha-proteobacterium, leading to symbiosis. Over time, most bacterial genes transferred to the nucleus, leaving reduced mtDNA.
Key evidence includes:
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Circular mtDNA like bacteria.
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70S ribosomes sensitive to chloramphenicol.
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Phylogenetic clustering with proteobacteria.
Why Not Other Options?
Fungi, protozoa, and algae are eukaryotes with bacterial-derived mitochondria, not sources. Sequence data rules out eukaryotic donors.
CSIR NET Relevance
This topic appears in Unit 2 (Cell Communication) for exams, testing endosymbiosis understanding. Mastery aids competitive prep in molecular biology.
