khai niem : dot bien lech boi la dot bien lam thay doi so luong NST o 1 hay 1so cap NST tuong dong.cac dang dot bien:the ko(2n-2),the mot(2n-1),the ba(2n+1),the bon(2n+2)...
Hau qua :lam mat can bang cua toan he gen __the lech boi thuong ko song duoc hay giam suc song,giam kha nag sinh san tuy loai.o nguoi gay hoi chung Dao(3NST so 21),tocno(1X)...
o thuc vat cung gap cac lech boi o ca va lua.