Grant Sutherland is renowned for pioneering work in human cytogenetics. In particular, he is interested in the cytogenetic and molecular characterisation of fragile sites on chromosomes, including the site responsible for fragile X syndrome — an inherited form of learning disability.

He was first to show that fragile site expression in white blood cells known as lymphocytes could be influenced by cell culture conditions such as the withdrawal of folic acid. He used this discovery to develop reliable methods for detecting rare folate-sensitive fragile sites, including that of fragile X syndrome.

In 2005, the Human Genetics Society of Australasia (HGSA) renamed their annual lecture in his honour. Grant received the Australia Prize for Molecular Science in 1998 and was awarded the Ramaciotti Medal for Excellence in Biomedical Research in 2001. He became a Companion of the Order of Australia in 1998. He is a past President of the HGSA and the Human Genome Organisation. He was named an all-time high achiever in medical research by the Australian National Health and Medical Research Council in 2013.