Munguva pfupi yapfuura, cytologists (cell biologists) vakafunga kuti chromosomes ndiyo yaive nhaka. Pakati pa1910 na1915, Thomas Hunt Morgan ne "Drosophilists" mu fly lab yake vakagadzira pfungwa mbiri idzi - zvese zvine nharo - mu "Mendelian-chromosome theory" yekugara nhaka. Vakaverenga huwandu hwezviitiko zvehukama hwehutano uye vakafungidzira kuti majini anogara pa chromosomes kunge ari pabhuruu; ivo vakafungidzira kutsanangurwa kwekuyambuka pamusoro pekukwegura uye kugadzirwa kwemajini evanhu vanobhururuka, iyo yakave muenzaniso unoshandiswa zvakanyanya muMendel's basa. Kubvira kuma1920s, nyanzvi dzezvekugadzira zvinhu zvakagamuchirwa zvakanyanya neWilliam H. Fisher, Hamilton uye M. Wright vakatevera pfungwa yehunhu hunoshanduka-shanduka hunoshanduka, iyo yakawanikwa nehunhu hunoshanduka-shanduka hunoshanduka hunoshanduka-shanduka hunoshanduka hunoshanduka-shanduka hunoshanduka hunoshanduka hunoshanduka-shanduka hunoshanduka hunoshanduka hunoshanduka hunoshanduka hun
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