[1] After graduating, Fruton encouraged her to specialize in nucleic acids, and in 1956 she joined the Laboratory of Biochemistry of Leon Heppel at the National Institutes of Health.

[8] In the wake of the 1973 report of the first use of recombinant DNA techniques to introduce genes from one species into another, Singer was among the first to call attention to the possible risks of genetic engineering.

[1] Her research with Leon Heppel on the role of enzymes that regulate synthesis of nucleic acids played a part in helping Marshall Nirenberg and Heinrick Matthaei to decipher the genetic code.

[16] These experiments allowed them to create a library of artificial RNA strands with defined sequences, such as a molecule made of only triplets of uracil that would code for phenylalanine.

During her time as the head of the Laboratory of Biochemistry at the National Cancer Institute in the 1980s, her research focused on LINEs, or long interspersed nucleotide elements.

[17] She studied the mechanism of how LINE-1 replicates and disperses copies to new locations in the genome, and found that the insertion of these elements could induce mutations in nearby genes, playing a role in genetic disease.

[1] When she was the co-chair of the Gordon Conference in 1973, she raised concerns over the potential health effects and risks in the relatively new field of recombinant DNA technology.