Kwayoyin halitta shine cikakken tsarin kwayoyin halitta, ciki har da kwayoyin halitta, a cikin kwayoyin halitta ko tantanin halitta. Dukkan bayanan kwayoyin halitta ne kwayoyin halitta suke gada daga iyayensu kuma suke yadawa zuwa ga zuriyarsu. Kwayoyin halitta sun ƙunshi DNA (deoxyribonucleic acid), wanda ke ƙunshe da umarni don haɓakawa da aikin kwayoyin halitta. Kwayoyin halitta na kowane nau'i ne na musamman, kuma bambance-bambance a cikin kwayoyin halitta na iya haifar da bambance-bambance a cikin halaye da halaye a tsakanin mutane a cikin jinsin.