Bayanin: Kodayake kwayoyin halitta suna dauke da dukkanin bayanan da kwayoyin halitta ke amfani da su don yin aiki, yanayin yana taka muhimmiyar rawa wajen tantance ainihin abubuwan da kwayoyin halitta ke nunawa. Kalmar "yanayi da kiwon lafiya" tana nufin wannan dangantaka mai dacewa. Halin da ake ciki na kwayoyin halitta ya dogara ne akan hulɗar kwayoyin halitta da yanayin. Misali mai ban sha'awa shine launin fata na Siamese cat. A wannan yanayin, yanayin jiki na cat yana taka muhimmiyar rawa na yanayin. Kwayoyin cat na launin gashi mai duhu, don haka ƙwayoyin da ke samar da gashi a cikin cat suna samar da sunadarai na salula wanda ke haifar da gashi mai duhu. Amma waɗannan sunadarai masu samar da gashi masu duhu suna da hankali ga yanayin zafi (watau suna da yanayin da ke haifar da yanayin zafi) kuma a cikin yanayin zafi mai zafi, yanayin da ke haifar da mummunar tasiri a wuraren da gashi yana da nau'in kwayoyin halitta da ke haifar da mummunar tasiri.
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