A tsakanin 1910 da 1915, Thomas Hunt Morgan da "Drosophilists" a cikin lab dinsa sun kirkiro wadannan ra'ayoyin guda biyu a cikin "Mendelian-chromosome theory" na gado. Sun ƙididdige abin da ake kira haɗin kwayoyin halitta kuma sun yi iƙirarin cewa kwayoyin suna zaune a kan chromosomes kamar yadda suke a kan beads; sun yi amfani da ra'ayoyin da suka dace don bayyana ƙetare da kuma gina nau'in kwayoyin halittar Drosophila melanogaster, wanda ya zama samfurin da aka yi amfani da shi a cikin aikin Mendel. Ba da daɗewa ba bayan haka, masu binciken kwayoyin halitta (masana ilimin kwayoyin halitta) sun ba da shawarar cewa chromosomes sune kayan gado. Daga farkon shekarun 1920 zuwa 1915, Thomas Hunt Morgan da "Drosophilists" a cikin lab dinsa sun yi amfani da waɗannan ra'ayoyin guda biyu - duka biyu masu rikitarwa - a cikin "Mendelian-chromosome theory" na gado. Sun yi amfani da ra'ayoyin da aka samo daga ra'ayin halittar halittar kwayoyin halitta, wanda ya fito daga ra'
ƙwayoyin halitta