. ▁Bo ots ma ▁had ▁a ▁special ▁interest ▁in ▁chrom os ome ▁ 2 2 , ▁which ▁was ▁recently ▁discovered ▁to ▁be ▁involved ▁in ▁chron ic ▁my el ogen ous ▁le uk emia . ▁In ▁ 1 9 8 2 , ▁the ▁research ▁team ▁of ▁Bo ots ma ▁discovered ▁the ▁cause ▁of ▁this ▁specific ▁type ▁of ▁blood ▁cancer : ▁two ▁broken ▁chrom os om es ▁( 9 ▁and ▁ 2 2 ) ▁which ▁were ▁attached ▁mistaken ly ▁re att ached ▁to ▁the ▁other , ▁leading ▁to ▁the ▁Philadelphia ▁chrom os ome . ▁ ▁Another ▁topic ▁on ▁which ▁Bo ots ma ▁further ed ▁research ▁from ▁his ▁time ▁at ▁T NO ▁was ▁DNA ▁repair . ▁He ▁set ▁up ▁research ▁into ▁gen etic ▁dis orders , ▁especially ▁x er oder ma ▁p ig ment os um ▁( X P ). ▁For ▁this ▁research ▁Bo ots ma ▁used ▁human ▁cells , ▁being ▁one ▁of ▁the ▁first ▁in ▁the ▁Netherlands ▁to ▁do ▁so . ▁With ▁the ▁developing ▁of ▁technology , ▁especially ▁the ▁possibility ▁to ▁insert ▁foreign ▁DNA ▁into ▁humans ▁and ▁the ▁discovery ▁of ▁recom bin ant ▁DNA , ▁Bo ots ma ▁was ▁able ▁to ▁further ▁his ▁study ▁of ▁XP . ▁In ▁ 1 9 8 4 ▁his ▁group ▁was ▁able ▁to ▁clone ▁the ▁repair ▁gene ▁ER CC 1 . ▁When ▁ER CC 3 ▁was ▁also ▁cl oned ▁this ▁led ▁to ▁a ▁solution ▁for ▁DNA ▁repair ▁in ▁XP - pat ients ▁by ▁inserting ▁them ▁in ▁their ▁fib ro bl asts , ▁leading ▁to ▁an ▁overall ▁further ed ▁the ▁understanding