[1] Mortelmans grew up in Ostend, Belgium, and moved to the United States in fall 1965 after her fiancé was accepted to Stanford University to a master's program in electrical engineering, and they married the following Christmas.
[2] She initially took Palo Alto High School to improve her skills as a typist at Kaiser Electronics and Aerospace, and continued her education after her husband graduated from Stanford and they moved to Sunnyvale so he could work at IBM.
[2] At Stanford, Mortelmans initially had enough prior credits to finish a degree in biology in two years, and found microbiology to be particularly fascinating.
She earned a degree in Medical Microbiology, and continued into the Ph.D. program there, focusing on Salmonella plasmids, eventually having one named after her, pKM101; that plasmid is a key component in the Ames test (named for Bruce Ames).
[2] After receiving her Ph.D. from Stanford, Bruce Ames directed Mortelmans to SRI International, where she was hired in 1976.