deletion

of a base pair
https://doi.org/10.1351/goldbook.09694

Loss of a part (one or more base pairs) of deoxyribonucleic acid (DNA).

Source:
PAC, 2018, 90, 1121. 'Terminology of bioanalytical methods (IUPAC Recommendations 2018)' on page 1144 (https://doi.org/10.1515/pac-2016-1120)