[2] Frommer then determined the chromosomal locations of the major simple-sequence repeats by devising a new method of non-radioactive labelling, based on incorporation of bromodeoxyuridine into single-stranded probes.
[citation needed] In 1984, Frommer spent a study leave in the laboratory of Adrian Bird, and took part in the characterisation of what were then termed HTF (HpaII Tiny Fragments) islands in mammalian genomes.
[4] She and her PhD student Margaret Gardiner-Garden were able to identify these genomic components by DNA sequence characteristics alone, without prior knowledge of methylation status, and gave them the name "CpG islands.
The PCR products of bisulphite reactions could be sequenced directly to measure the extent of methylation at any CpG site in a population of DNA molecules.
[8][9] Frommer and her colleagues have also developed a powerful model system to study the molecular biology of behavioural characteristics and evolutionary processes using native Australian fruit flies,.