Alexander Kotznok (later Keynan) was born in Kiev, Ukraine to Rachel and Ephraim Kotznok (1883–1963), an industrialist, insurance agent and an active Zionist. In 1930, Keynan immigrated with his family to Mandate Palestine. He studied for a M.Sc and Ph.D. at the Hebrew University, graduating in 1950. His thesis was on the biological and biochemical studies of Clostridium botulinum. He served in the science department of the Haganah.
In 1945, Keynan married Malka Ben-Zvi. The couple had two daughters. His paternal aunt was Bracha Peli.
Scientific and academic career
In 1948, with the establishment of the Israel Defense Forces, Keynan joined the Science Corps (חיל המדע) and thereafter was a founding member of the Israel Institute for Biological Research in Ness Ziona and its first director. Keynan served as the Chief Scientific Director of the Institute and the director of the Institute of bacteriology.
In 1964, Keynan was appointed to the chairman position of the National Council for Research and Development (Hebrew: המועצה הלאומית למחקר ופיתוח אזרחי). In 1967 Keynan was appointed as the head of the Institute of Life Sciences (המכון למדעי החיים) at the Hebrew University. During this period he was appointed as a member of the Atomic Energy Commission (הוועדה לאנרגיה אטומית).