Question: A form of dwarfism known as Ellis–van Creveld syndrome was first discovered in the late 1930s, wh…

A form of dwarfism known as Ellis–van Creveld syndrome was first
discovered in the late 1930s, when Richard Ellis and Simon van
Creveld shared a train compartment on the way to a pediatrics
meeting. In the course of conversation, they discovered that they
each had a patient with this syndrome. They published a description
of the syndrome in 1940. Affected individuals survive but have a
short-limbed form of dwarfism and often have defects of the lips
and teeth, and polydactyly (extra fingers). The largest pedigree
for the condition was reported in an Old Order Amish population in
eastern Pennsylvania by Victor McKusick and his colleagues (1964).
In that community, about 5 per 1000 births are affected, but in the
population of 8000, the observed frequency is 2 per 1000. All
affected individuals have unaffected parents, and all affected
cases can trace their ancestry to Samuel King and his wife, who
arrived in the area in 1774. It is known that neither King nor his
wife was affected with the disorder. There are no cases of the
disorder in other Amish communities, such as those in Ohio or
Indiana.

Calculate the frequency of heterozygotes in the community,
assuming Hardy-Weinberg conditions.