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Nonneutral mitochondrial DNA variation in humans and chimpanzees
M W Nachman1, W M Brown, M Stoneking
1Section of Genetics and Development, Cornell University, Ithaca, New York 14853, USA.
Genetics
|March 1, 1996
Summary
Mitochondrial DNA (mtDNA) variation in humans and chimpanzees shows more replacement than silent mutations, contradicting neutral evolution. This suggests many mitochondrial DNA polymorphisms may be slightly harmful.
Area of Science:
- Evolutionary biology
- Molecular evolution
- Genetics
Background:
- Neutral theory posits that most molecular variations are selectively neutral.
- Mitochondrial DNA (mtDNA) is frequently used to study molecular evolution due to its unique inheritance and mutation patterns.
Purpose of the Study:
- To investigate whether patterns of human and primate mitochondrial DNA variation align with the neutral model of molecular evolution.
- To determine if selection pressures differ within species compared to between species.
Main Methods:
- Sequencing of the NADH dehydrogenase subunit 3 (ND3) gene in humans, chimpanzees, and gorillas.
- Reanalysis of published human restriction fragment length polymorphism (RFLP) data for the entire mitochondrial genome.
- Comparison of complete mitochondrial DNA sequences from three human individuals.
Main Results:
- The ratio of replacement to silent nucleotide substitutions was higher within humans and chimpanzees than between species.
- Analysis of both ND3 gene sequences and RFLP data revealed this elevated replacement-to-silent substitution ratio within humans.
- This pattern was observed across multiple human mitochondrial genes, inconsistent with neutral evolution.
Conclusions:
- The observed patterns of mitochondrial DNA variation are inconsistent with a strictly neutral model of molecular evolution.
- Data suggest that many mitochondrial protein polymorphisms are slightly deleterious.
- Findings align with previous studies linking mitochondrial DNA variations to human diseases.