Gregg Johnson received his master's degree in genetic toxicology and doctoral degree in the area of plant cytogenetics. Since beginning his teaching career at Bethel in 1975, he has taken sabbaticals at the Mayo Clinic (human cytogenetics), studying chromosomal abnormalities and cancer, and the University of Minnesota (plant cytogenetics), studying somaclonal variation and chromosome isolation in corn tissue culture .

His interests are in genetic toxicology using human cell culture and sister chromatid exchange techniques; cell culture and cytogenetic analysis of plants, particularly crop grain plants; and animal behavior, particularly the role of sex hormones in gender-specific behavior.

He teaches BIO114D Introduction to Biodiversity, Ecology, and Adaptation, BIO103D Human Biology, BIO322 Animal Behavior, BIO361 Plant Taxonomy and Ecology, GES321K Human Genetics. and BIO366 Plant Physiology.