Final answer:
Cytochrome c is a better marker for studying evolutionary relatedness of organisms than hemoglobin because it is more conserved due to its crucial role in the cell's electron transport chain. Its sequence remains similar across different species, reflecting their common ancestry, which allows scientists to assess evolutionary kinship.
Step-by-step explanation:
The Evolutionary Significance of Cytochrome c
Cytochrome c is a highly conserved protein involved in the electron transport chain critical for cellular energy production. Due to its essential role in the cell, it has experienced very little change over millions of years, making it an excellent marker for studying evolutionary relatedness among species. In contrast, hemoglobin, which varies more among species, is not as reliable for phylogenetic studies. This makes cytochrome c a better choice for assessing evolutionary kinship. The amino acid sequence of cytochrome c often remains highly similar even across greatly divergent species, reflecting their common ancestry.
For example, human cytochrome c and chimpanzee cytochrome c show no differences in protein sequence, indicating a very recent common ancestor. In contrast, differences between human and rhesus monkey cytochrome c are minimal, showing only a single amino acid variance. Further away on the evolutionary tree, humans and yeast have differences in 44 amino acids in their cytochrome c, suggesting a much older common ancestor compared to that with mammals. Therefore, by analyzing the amino acid sequence of cytochrome c across various organisms, scientists can infer the evolutionary history and the degree of relatedness between species.