Nuclear DNA—passed on by fathers and mothers—has only a single trace of DNA.
(Get a DNA overview.)
Ancient nuclear DNA has never been connected between two mummies, experts say.
But if scientists come up empty comparing the fetuses to Tut, they could still examine the mitochondrial DNA of several unidentified female mummies.
Earlier this year archaeologists moved two mummies found in the pose of royal women from the Valley of the Kings for further study.
Archaeologists also are studying two nonroyal female mummies in addition to known mummies such as Tut and his great grandmother Tuya.
Several 18th-dynasty (1550 to 1069 B.C.) queens including Tiye, Nefertiti, and Kiya have not been identified.
It will be many months or even years before the DNA tests are complete.
The fetuses' fragile bones and air contamination may slow the process, experts say.
"The bones [of fetuses] are more brittle, because they weren't completely formed," said Angelique Corthals of Stony Brook University in New York.
"External contamination is going to be a huge problem."
The fetus mummies have likely been corrupted since they were discovered in Tut's tomb in 1922. The specimens were kept in a Cairo hospital in the early 1930s before being moved to Cairo University, where they have resided for more than 70 years.
"We have one that is in fairly acceptable shape and one that it is bad shape," said Ahmed Sameh, dean of the Faculty of Medicine at Cairo University.
Studying ancient mummy fetuses is part of a larger recent effort by Egyptian scientists and archaeologists to identify all of the mummies found in Egypt.
(Related: "Egypt's Female Pharaoh Revealed by Chipped Tooth, Experts Say" [June 27, 2007].)
These two fetuses will be studied at a new ancient-DNA lab opening at Cairo University to supplement research at a similar lab at the Egyptian Museum.
"You have to make two [DNA laboratories] for comparison to have accurate information," Hawass said. "You cannot depend on the result of one lab."
The new lab is expected to lend credibility to the project, which has not yet published results.
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