Final answer:
The evolution of the β-globin chain, including the mutation in sickle cell anemia, showcases the detailed relationship between DNA, RNA, and protein structure, and how genetic variability can lead to significant changes in protein function.
Step-by-step explanation:
The evolution of the β-globin chain is a prime example of how small genetic changes can result in significant functional differences in proteins, illustrating the evolutionary process on a molecular level. For instance, the mutation leading to sickle cell anemia involves a single amino acid substitution in the hemoglobin β chain: valine replaces glutamic acid. This change of one amino acid among the approximate 600 in the hemoglobin molecule is caused by a single nucleotide alteration within the DNA, demonstrating how precise the genetic code correlates with protein structure and function. Conservation of the genetic code across different species highlights the shared common origin of life on Earth, with the code being so universal that, hypothetically, mRNA from a horse could be inserted into a tulip, and the tulip would produce horse globin.
Evolution has likely favored the expansion of protein functionality through mechanisms such as the repetition of simpler domains and genetic recombination. A significant portion of the genetic code evolution has been proposed to co-originate from the synthesis of proteins and nucleic acids in primitive cells. This hypothesis, and others like it, enrich our understanding of how complex biological macromolecules have evolved over time.