Passage II

In red blood cells (RBCs), the protein hemoglobin (Hb) carries oxygen. Each Hb molecule contains 4 globin polypeptides一a pair of P-type globins and a pair of Q-type globins. The possible combinations of the P-type globin and the Q-type globin for the 3 variants of human Hb are shown in Table 1. For each combination, the notation is of the form (P-type)2(Q-type)2.

Figure 1 shows the sites of RBC production during early human development (gestation through 48 weeks after birth). The figure also shows, over that time period, what percent of the total number of globin polypeptides produced are ζ, ε, γ, α, β, or δ globin polypeptides.

Table and figure adapted from Robert L. Nussbaum, Roderick R. Mclnnes, and Huntington F. Willard, Thompson & Thompson Genetics in Medicine, 6th edition. @2004 by Elsevier.

8. The percent of any particular globin polypeptide produced in the RBCs of a human does not change significantly after the first 48 weeks of age. Based on this information and the information provided in the passage, the most abundant Hb variant in a healthy 2-year-old child would most likely have what globin polypeptide combination?

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

From the question, there is no difference in globin polypeptide between 2-year-old and 48-week-old children. It can be seen from Figure 1 that at 48 weeks of birth, α globin accounts for 50%, and β globin accounts for about 48%, so option F is the most suitable