Final answer:
In an autosomal recessive disease, the term "2pq" in the Hardy-Weinberg equation represents carriers of the disease. They have one copy of the recessive allele and one normal allele, and they do not exhibit symptoms of the disease but can pass the allele to their offspring.
Step-by-step explanation:
In an autosomal recessive disease, the people represented by the "2pq" figure in the equation "p2 + 2pq + q2" are carriers of the disease. These individuals carry one recessive allele and one dominant allele for the disease (heterozygous) but do not exhibit the symptoms. In the case of cystic fibrosis, for instance, carriers are represented by a heterozygous genotype (Ff), whereas those affected by the disease are homozygous recessive (ff).
Autosomal recessive disorders, such as cystic fibrosis or sickle cell anemia, only manifest in individuals who receive two copies of the recessive allele, one from each parent. Carriers, having only one copy of the recessive allele, do not show any symptoms of the disease because they also have a normal allele that provides a protective effect. Thus, when two carrier parents mate, there is a 25% chance for an affected offspring (ff), a 50% chance for a carrier offspring (Ff), and a 25% chance for an offspring with two normal alleles (FF).