Suppose there are 50 couples with the same blood type and hemoglobin genotypes. They live on a small, isolated Pacific island on which very few mosquitoes have been identified. All the individuals are heterozygous for type A blood and have sickle cell trait. The 50 couples had 224 children over the years. The children were all tested for blood type and for the presence of the sickle cell allele.

Here are the results. Testing Results Blood Test Results Number of Children Type A, normal RBCs 48 Type O, normal RBCs 18 Type A, sickle cell trait 92 Type O, sickle cell trait 33 Type A, sickle cell disease 27 Type O, sickle cell disease 6 Are these data significant? Explain using a chi-square statistical analysis test.

a. What is χ2 ?

b. Calculate df.

c. Using the critical values table, determine the P value.

d. Interpret the P value as it relates to these data. Explain the significance.

From what you know about hemoglobin, sickle cell disease, and blood type, what selection pressure is acting on this population of children and causing the null hypothesis to be rejected? Explain your answer. (Hint: Look at the actual differences between the observed and expected numbers.)