Read the following passage and answer the questions that follow. According to evolutionary theory, every evolutionary change involves the substitution of a new gene for the old one and the new allele arises from the old one. Continuous accumulation of changes in the DNA coding for proteins leads to evolutionary differences. The chemical composition of DNA is basically the same in all living beings, except for differences in the sequence of nitrogenous bases. Given below are percentage relative similarities between human DNA and DNA of other vertebrates :

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CASE_STUDIESMolecular Evidence for EvolutionCBSE PYQ4 sub-questions

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CASE_STUDIESMolecular Evidence for Evolution

Highly conserved proteins such as Haemoglobin and Cytochrome-C provide the best biochemical evidences to trace evolutionary relationships between different groups. Cytochrome-C is formed of 104 amino acids. Cytochrome-C is the respiratory pigment present in all eukaryotic cells. It has evolved at a constant rate during evolution. In chimpanzees and humans, Cytochrome-C genes are identical. The given data shows the evolution of the Cytochrome-C gene in different mammals from kangaroos, cows, rodents to humans : | Groups | Nucleotide substitution in the gene of Cytochrome-C | Millions of years ago | |--------|-----------------------------------------------------|----------------------| | Human/Kangaroo | 100 | 125 mya | | Human/Cow | 75 | 120 mya | | Human/Rodent | 60 | 75 mya |