Dr. Mary Claire King, a geneticist at the University of Washington who discovered the role of certain genetic mutations in breast cancer, said that because of Dr. Motulsky’s work in medical genetics, “the field is now integrated into every other field of medical practice, and has become the soul of precision medicine.”

Dr. Motulsky’s research encompassed genetic contributions to a broad array of conditions, including heart disease, blood disorders, colorblindness, infections and immunity, hypertension and alcoholism. He studied genetic disorders linked to certain population groups, like Ashkenazi Jews, and considered the ethical issues raised by genetic testing and gene therapy.

He was also highly esteemed as a mentor, becoming the subject of a chapter in a 2009 book on mentoring in higher education.

One who studied with him was Dr. Joseph L. Goldstein. It was during a fellowship with Dr. Motulsky, beginning in 1968, that Dr. Goldstein laid the foundation for research on how the body processes cholesterol. The findings led to a Nobel Prize in Physiology or Medicine in 1985, which Dr. Goldstein shared with Dr. Michael S. Brown. Their work led to the development of cholesterol-lowering statin drugs.

“Arno was sort of a maestro of human genetics,” Dr. Goldstein, now chairman of the department of molecular genetics at the University of Texas Southwestern Medical Center in Dallas, said in an interview. He added in an email, “He gave me the confidence to design a large study on lipid levels in survivors of heart attacks and gave me support and resources — at a time when I was only 28 years old.”

Arno Gunther Motulsky was born on July 5, 1923, in Fischhausen, Germany, on the Baltic Sea, to Herman Motulsky, a shopkeeper, and the former Rena Sass.

His parents tried to leave Germany with him and his younger siblings, Leah and Lothar, in 1939, before war broke out in Europe. In an account he gave to the Annual Review of Genomics and Human Genetics in 2016, Dr. Motulsky said his family had hoped to join his father’s brother in Chicago but headed for Cuba instead after hearing that a United States quota system was causing long delays in granting visas.