AP Biology :1.7 Proteins - Exam Style questions with Answer- FRQ
Question
TOPIC 1.7 Proteins
(a) TOPIC 6.7 Mutations
(b) TOPIC 6.7 Mutations
The table below shows the amino acid sequence of the carboxyl-terminal segment of a conserved polypeptide from four different, but related, species. Each amino acid is represented by a three-letter abbreviation, and the amino acid residues in the polypeptide chains are numbered from the amino end to the carboxyl end. Empty cells indicate no amino acid is present.
(a) Assuming that species I is the ancestral species of the group, explain the most likely genetic change that produced the polypeptide in species II and the most likely genetic change that produced the polypeptide in species III.
(b) Predict the effects of the mutation on the structure and function of the resulting protein in species IV. Justify your prediction.
Answer/Explanation
Ans:
(a) Assuming that species I is the ancestral species of the group, explain the most likely genetic change that produced the polypeptide in species II and the most likely genetic change that produced the polypeptide in species III. (2 points maximum)
Explanation: 1 point per row
NOTE: Specific names of mutation types are not required.
(b) Predict the effects of the mutation on the structure and function of the resulting protein in species IV. Justify your prediction. (2 points maximum)
(a) In species 2, the most likely genetic change was a point mutation, in which a single nucleotide is altered, which changes the amino acid being coded for. In species 3, the most likely genetic change was a point mutation that coded for a STOP codon, which halted production of the polypeptide prematurely.
(b) The protein produced in species 4 will have a much different structure, and the function will be radically different. The frameshift mutation that resulted in the polypeptide completely altered the polypeptide chain, which in turn will change the intersections between amino acids, so the structure is changed. The altered amino acid segnence will cause the protein’s function to shift.