1. High Conservation and Variability:
* Conservation: Cytochrome c's structure and function are remarkably conserved across diverse species. This means the amino acid sequence of cytochrome c has remained largely unchanged over millions of years of evolution. This conservation highlights the importance of this protein for basic cellular processes.
* Variability: While highly conserved, cytochrome c does exhibit some variability in its amino acid sequence. This variability arises from mutations that accumulate over time. The number of differences in the amino acid sequence between two species is directly related to the evolutionary distance between them.
2. Molecular Clock:
* The rate of mutation in cytochrome c is relatively constant. This allows scientists to use the number of amino acid differences as a "molecular clock" to estimate the time since two species diverged from a common ancestor.
3. Phylogenetic Analysis:
* By comparing the amino acid sequences of cytochrome c across different species, scientists can construct phylogenetic trees that show the evolutionary relationships between organisms.
* These trees often align well with traditional classifications based on morphology and other characteristics, providing strong support for the theory of evolution.
Examples of Cytochrome c's Evolutionary Significance:
* Human and Chimpanzee: Cytochrome c in humans and chimpanzees differs by only one amino acid, reflecting their close evolutionary relationship.
* Human and Yeast: Cytochrome c in humans and yeast differs by 43 amino acids, reflecting a more distant evolutionary relationship.
Key Points:
* The remarkable conservation of cytochrome c across diverse species is strong evidence for its importance in cellular respiration and for the shared ancestry of life on Earth.
* The subtle variations in cytochrome c sequences provide valuable information about evolutionary relationships between species and the timing of their divergence.
Cytochrome c is a classic example of how biochemical evidence can be used to study evolutionary relationships and provides powerful support for the theory of evolution.
