▁March ▁ 6 , ▁ 2 0 1 4 ▁( the ▁procedure ▁is ▁also ▁itself ▁illegal ▁with ▁very ▁limited ▁exceptions ). ▁In ▁the ▁UK , ▁working ▁ter riers ▁can ▁still ▁be ▁shown ▁with ▁dock ed ▁t ails , ▁but ▁dogs ▁kept ▁as ▁p ets ▁cannot . ▁ ▁Health ▁▁ ▁A ▁gen etic ▁test ▁is ▁available ▁for ▁progress ive ▁ret inal ▁at ro phy ▁( type ▁cr d 3 ), ▁a ▁con gen ital ▁dis order ▁that ▁gradually ▁results ▁in ▁blind ness ▁beginning ▁at ▁about ▁five ▁years ▁of ▁age . ▁As ▁blind ness ▁from ▁this ▁cause ▁did ▁not ▁become ▁apparent ▁until ▁well ▁into ▁the ▁bre eding ▁years , ▁it ▁was ▁difficult ▁to ▁bre ed ▁out ▁this ▁trait ▁before ▁the ▁advent ▁of ▁the ▁test . ▁Comple t ely ▁elimin ating ▁the ▁defect ive ▁gene ▁will ▁be ▁tricky ▁even ▁now , ▁as ▁bre eding ▁only ▁clear - to - clear ▁would ▁sever ely ▁restrict ▁choices ▁in ▁an ▁already ▁small ▁gene ▁pool . ▁It ▁is ▁straightforward , ▁however , ▁to ▁produce ▁lit ters ▁that ▁will ▁never ▁be ▁affected ▁by ▁this ▁type ▁of ▁P RA , ▁even ▁though ▁some ▁individuals ▁in ▁the ▁l itter ▁may ▁carry ▁the ▁gene . ▁( B ecause ▁the ▁trait ▁is ▁re cess ive , ▁animals ▁with ▁only ▁one ▁copy ▁of ▁the ▁defect ive ▁gene ▁do ▁not ▁develop ▁P RA , ▁and ▁it ▁is ▁necessary ▁only ▁that ▁one ▁parent ▁be ▁clear ▁to ▁achieve ▁this .) ▁Res p ons ible ▁bre ed ers ▁use ▁the ▁test ▁to ▁plan ▁P RA - free ▁lit ters ▁and