Question

table 1: sickle cell hemoglobin mutation

	normal hemoglobin	mutated hemoglobin
partial amino acid sequence	pro-glu-glu	pro-val-glu
hemoglobin structure	normal	abnormal
rbc shape in low-oxygen conditions	normal	sickle-shaped

which statement best describes the connection between the hemoglobin gene sequence and sickle - shaped rbcs?

a. several changes to the dna sequence lead to an abnormal hemoglobin protein, which causes rbcs to change shape under low - oxygen conditions.

b. low - oxygen conditions cause the hemoglobin gene to mutate, which then changes the protein structure of hemoglobin.

c. a single mutation in the dna sequence changes an amino acid in the hemoglobin protein, which causes rbcs to change shape under low - oxygen conditions.

d. low - oxygen conditions cause the hemoglobin protein to change shape, which then causes the hemoglobin gene to mutate.

Explanation:

• Analyze Option A: The DNA sequence has one change (GAG→GTG), not several. Eliminate A.
• Analyze Option B: Mutations in DNA (not low - oxygen) cause protein changes. Low - oxygen affects RBC shape, not gene mutation. Eliminate B.
• Analyze Option C: The DNA sequence has one mutation (GAG→GTG), changing Glu to Val in the amino acid sequence. This abnormal hemoglobin causes RBCs to sickle in low - oxygen. This matches the table.
• Analyze Option D: Low - oxygen doesn't cause the gene to mutate. It affects RBC shape due to abnormal hemoglobin. Eliminate D.

Answer:

C. A single mutation in the DNA sequence changes an amino acid in the hemoglobin protein, which causes RBCs to change shape under low - oxygen conditions.