The usefulness of amniocentesis was limited until the 1960s because?

Question

The usefulness of amniocentesis was limited until the 1960s because:


before then, there was no way to visualize chromosomes

it was too expensive for anyone to afford

ethical concerns prevented the extraction of fetal cells

the correct number of human chromosomes was not determined until the 1950s

before then, it was not known that a fetus sloughed off epidermal cells

Answer 1

Most of the answers can be crossed off just for being not even close.

Chromosomes were first found in 1842, and the chromosomal theory of inheritance was fairly well worked out and accepted by 1925.

While ethics and expense in many ways STILL are concerns, it didn't stop people from performing the procedure as early as 1877, and it doesn't stop people now. So these are probably out.

That leaves only your last option. And, in fact, it wasn't until 1966 that it was demonstrated that cultured cells from an amniocentesis could by typed and that the results corresponded to the fetus. Later research (and some before that didn't involve genetics) demonstrated that any number of diseases could be diagnosed using amniocentesis, and it was this more than anything that contributed to its popularity.

Hope that helps!