Although initially interested in becoming a veterinarian, but talked out of it by her father, Elizabeth Nesta (Pat) Marks took up science at the University of Queensland. She graduated in 1938 with Second Class Honours in Zoology. Unable to take up Honours in entomology (a course reserved for agriculture graduates), Marks went on to study parasitology under the supervision of Dr Ronald Hamlyn Harris (a one-time Brisbane City entomologist). Her project was varied and included preparing a card index of all the parasites of Australian marsupials and a study of the life history of the mosquito. This was the start of her long and fruitful research career in mosquitoes and mosquito-borne diseases.

Her Honours project was of such high quality that it was automatically converted to a Masters Degree which was conferred in 1940. Marks then took up a post as an assistant curator at Queensland University's pathology museum and also demonstrated in the medical school for Mr Perkins (entomologist and lecturer). With the outbreak of war there were also outbreaks of malaria and dengue fever in Cairns and the tropics, so Perkins was employed by the Australian Army to train select members at the army malaria control schools. Marks was brought in to assist with the collection of material for these training classes. Then in 1943 the university established the Mosquito Control Committee (MCC), with Perkins as Secretary, to study Queensland mosquitoes and Pat Marks successfully applied for the post of MCC Graduate Research Assistant. She remained with the MCC until it was dissolved by the government in 1973 and during this time undertook numerous field trips and made many new discoveries.

In 1949 Pat Marks went to Europe for a ten month study trip and then decided to enrol in a Doctor of Philosophy (PhD) in insect physiology at the University of Cambridge. During this time she also joined the Royal Entomological Society of London. Upon completing her PhD, Marks returned to Australia and the MCC (1951). She was soon dispatched to Victoria as an assistant to Dr Bill Reeves who was in Mildura carrying out field research on the then current outbreak of Murray Valley Encephalitis. In 1952 Marks was also sent to Townsville in Queensland to investigate an outbreak there and later went to some of the islands of the north coast, in the Torres Straits. From 1951 to 1973 she also ran a number of other projects which included the study of the insects used by the CSIRO (Commonwealth Scientific and Industrial Research Organisation) Wildlife Survey Section for the introduction of myxomatosis in rabbits, a collaboration with the Queensland Institute of Medical Research which included her collecting widely throughout rural Australia and the Torres Strait Islands, and she trained many of Queensland's health inspectors.

After the MCC closed down, Marks was transferred to the Queensland Institute of Medical Research where she was appointed Principal Entomologist. She officially retired in 1983 but remained on at the Institute to continue her work. The results of Mark's many studies and field trips led to the production of major publications including the Atlas of Common Queensland Mosquitoes (1966) and the twelve volume set The Culicidae of Australasia (1980-1989). Her work also led to major breakthroughs and the discovery of at least thirty-eight new mosquito species, as well as new species of other insects including fruit flies, bugs, cockroaches and ticks. Marks was also a long-term and active member of the Queensland Naturalists Club with whom she helped preserve the Bora rings (indigenous ceremonial sites) in Samford, south-eastern Queensland. In 1990 Patricia Marks was appointed a Commander Officer of the Order of Australia (AO) for her services to science, particularly entomology.