Hydatid mole is a type of pregnancy that, without medical intervention, frequently results in the death of the mother. The hydatid mole is thought to result most often from an abnormality in fertilization, such that the egg has two copies of paternal chromosomes, and no maternal DNA. A fetus fails to develop; instead there is rapidly growing chorionic tissue in the placenta, which secretes hCG

Question

and thus leads to a positive pregnancy test and outward signs of pregnancy. The first clue to the obstetrician that the pregnancy is abnormal is often the lack of a heartbeat in the first trimester.

A. What is the genotype of the hydatid mole tissue? From the genotype alone, would most science -literate
students predict that a normal embryo would form? Explain, indicating what this suggests about maternal
and paternal contributions to the embryo.
B. The most common cause of molar pregnancy-related maternal death is a type of cancer called
choriocarcinoma, with the hydatid mole being the source and thus resembling a tumor. What characteristic
of tumors leads to cancer?
C. While these pregnancies often spontaneously abort, some women may elect to terminate a hydatid molar
pregnancy. Is this a special case of elective abortion or is it tumor-removal? Explain.

Answer 1

A. The genotype would be 46XX or 46XY; 46YY is not viable at all because the essential genes on the X chromosome
are missing. These genotypes are normal, so it is unclear why a fetus does not form. This suggests that there is
some contribution of the maternal nucleus to development apart from just the chromosome number.
B. It is metastasis, or spread of abnormal cells due to loss of cell adhesion, that causes cancer.
C. Answers are based in part on personal opinion and will vary; if students consider primarily that this pregnancy
does not produce a fetus at all, they may argue that removal of this tissue is more like tumor removal than aborting
a person.