Casein is the major food protein found in mammalian milk and its amino acid sequ
ID: 219253 • Letter: C
Question
Casein is the major food protein found in mammalian milk and its amino acid sequence is very similar to a group of proteins called SPARCs found in both vertebrates and invertebrates. Both SPARCs and casein bind to calcium ions, and are involved in bone deposition in all bony animals, including like fish. The tree above shows the relationships of three SPARC family proteins based on amino acd similarity Referring to the tree, which of the following statements about the evolution of casein is most correct: worm SPARC cow cow SPARC Casein O A duplication of the SPARC-encoding gene resulted in a new gene that evolved a different function in early mammals ?b. Non-mammals lost the casein-encoding gene that they inherited from the last common ancestor of animals. c. There are only so many ways a protein can bind calcum ions, so the sequence match is due to convergence d. A mutation in the SPARC-encoding gene resuited in the evolution of a new protein with a different function. Click Sove and Submit to save and submit Click Sove All Answers to sove oll onswersExplanation / Answer
Caseins are the proteins that have evolved in the family of early mammals. As it is known, casein genes belong to family of secretory calcium-binding phosphoprotein (SCPP). This gene family has developed from SPARCL1 (SPARC-like 1) genes which were found in early vertebrate. The given cladogram suggests that there is duplication of SPARC encoding gene which resulted in a new gene in early mammals. The remaining options do not justify the given condition.