Question

Classical MHC molecules function as peptide-binding receptors that

present these peptides to : T cells for recognition by : T-cell receptors. MHC
molecules can be detected as far back in evolution as sharks, the same time at which Tcell
receptors can be identified. Examination of shark MHC proteins indicates that these molecules likely function identically to human MHC molecules. This conclusion is based on:

A. The conservation of amino acid residues important in peptide binding in both shark and human MHC proteins
B. The observation that MHC genes are highly polymorphic in sharks as well as humans
C. The fact that sharks have both MHC class I and MHC class II molecules
D. The finding that sharks have both classical and nonclassical MHC molecules, like humans
E. The ability to trace the evolution of MHC protein sequences from the earliest vertebrates to humans

Answer 1

The conclusion that shark and human MHC molecules function identically is based on the conservation of crucial amino acid residues and the presence of both MHC class I and II molecules, as well as polymorphism in MHC genes in sharks. The correct option is C.

Step-by-step explanation:

The examination of shark MHC proteins suggests that they likely function identically to human MHC molecules. This conclusion is primarily based on the conservation of amino acid residues important in peptide binding in both shark and human MHC proteins.

Additionally, sharks have both MHC class I and MHC class II molecules, and their MHC genes are as highly polymorphic as those found in humans, indicating a sophisticated level of immune response and functionality similar to human MHC mechanisms.

Moreover, like humans, sharks possess both classical and nonclassical MHC molecules, further supporting the shared evolutionary origin and functional conservation of these immune system components. The correct option is C.