Describe the hypothesis that James Neel proposed to describe the inheritance pattern of SCD. What ...

In 1949, James Neel identified the inheritance pattern of SCD in a study that examined
42 parents of children with SCD. None of these parents had SCD. Neel was testing the genetic hypothesis that SCD is produced by a recessive allele and that the parents of children with SCD
are heterozygous carriers. He reasoned that if his hypothesis were correct, all the parents of SCD patients would show evidence of a low level of sickle-shaped red blood cells. In Neel's tests, the blood of all 42 parents of SCD patients displayed a small number of sickle-shaped red blood cells, confirming the hypothesis that the inheritance of SCD is explained by the presence of two alleles
in heterozygous carrier parents. The validation of Neel's hypothesis confirms that in SCD families, two alleles, A and S, can occur at the -globin gene, and that there are three genotypes, AA (homozygous wild type), AS (heterozygous carrier), and SS (sickle cell disease). The hypothesis predicts that when two heterozygous carriers produce a child, the likelihood of the child having SCD is 1 in 4.