Duk wani jariri da aka haifa daga haduwa: na oocyte a bangaren uwa da maniyyi a bangaren uba. Kowannensu yana kawo nasu kayan gado:

• 22 chromosomes + chromosome X guda don oocyte
• 22 chromosomes + wani X ko Y chromosome don maniyyi

Haki yana haifar da kwai da ake kira zygote, asalin kwayar halitta wanda a cikinsa suka haɗu da chromosomes na uwa da na uba. Kwayar halittar ta cika: 44 chromosomes da 1 nau'i na chromosomes na jima'i. Daga haɗuwa tsakanin kwai da maniyyi, saboda haka an riga an ƙayyade duk halayen yaron: launin idanunsa, gashinsa, siffar hancinsa, da kuma jima'i.

• idan maniyyi ya kasance mai ɗaukar chromosome na X, jaririn yana ɗaukar XX biyu: zai zama yarinya.
• idan ya ɗauki chromosome na Y, jaririn zai sami XY biyu: zai zama namiji.

Don haka jima'i na jariri ya dogara kacokan akan kwatsam, dangane da wanne maniyyi ne zai yi nasarar fara hadi da oocyte.

Daga mako na 6 na ciki, ana sanya sel na jima'i na farko a wurin da ovaries ko gwaje-gwaje zasu ci gaba daga baya. Amma ko da an riga an daidaita shi ta hanyar kwayoyin halitta, a wannan mataki jima'i na tayin ya kasance ba tare da bambanci ba. A cikin samari, azzakari yana bayyana a mako na 12 na ciki (14 WA – 3rd month), kuma a cikin 'yan mata, farji yana farawa a mako na 20 na ciki (22 WA, 5th month) (1). Saboda haka a cikin na biyu ciki duban dan tayi (morphological duban dan tayi na 22 makonni) yana yiwuwa a san jima'i na jariri.

• hanyar Shettles

A cewar aikin masanin halittu na Amurka Landrum Brewer Shettles, marubucin Yadda Zaka Zabi Jima'in Jaririnka2 (Yadda za a zabi jima'i na jariri), maniyyi mai dauke da chromosome na mace (X) yana ci gaba a hankali da kuma rayuwa mai tsawo, yayin da maniyyi mai dauke da chromosome (Y) ya ci gaba da sauri amma ya tsira. Don haka ra'ayin shine a tsara jima'i bisa ga jima'i da ake so: har zuwa kwanaki 5 kafin ovulation don inganta mafi yawan spermatozoa don samun 'ya mace; a ranar ovulation da kwanaki biyu masu zuwa don inganta maniyyi mafi sauri ga yaro. Don wannan an kara da wasu tukwici: pH na mahaifa gamsai (alkaline tare da yin burodi soda farji douche ga yaro, acidic tare da vinegar shawa ga yarinya), zurfin da axis na shigar azzakari cikin farji, gaban mace inzali ko a'a, da dai sauransu. Dr. Shettles ya ba da rahoton kashi 75% na nasara… ba a tabbatar da kimiyya ba. Bugu da ƙari, sababbin hanyoyin nazarin maniyyi ba su nuna wani bambanci a cikin jiki ko gudun motsi tsakanin X ko Y (3).

• hanyar baba

Dangane da binciken (4) da aka gudanar a cikin 80s a asibitin haihuwa na Port-Royal akan mata masu juna biyu 200, wannan hanyar Dr François Papa ya ƙera shi kuma ya ba jama'a gabaɗaya a cikin littafi (5). Ya dogara ne akan abincin da ke samar da wasu gishirin ma'adinai a cikin ma'auni mai kyau dangane da jima'i da ake so. Cin abinci mai arziki a cikin calcium da magnesium zai canza pH na farji na mace, wanda zai toshe shigar Y spermatozoa cikin kwai, don haka yana ba da damar samun 'ya mace. Sabanin haka, cin abinci mai arziki a sodium da potassium zai toshe shigar da maniyyi X, yana inganta damar samun ɗa. Dole ne a fara wannan tsauraran abinci aƙalla watanni 2 da rabi kafin ɗaukar ciki. Marubucin ya gabatar da adadin nasara na 87%, ba a tabbatar da shi ta hanyar kimiyya ba.

Wani bincike (6) da aka gudanar tsakanin 2001 da 2006 a kan mata 173 ya yi nazari kan ingancin abincin ionic hade da jadawalin jima'i daidai da ranar haihuwa. An yi amfani da su daidai da haɗuwa, hanyoyin biyu sun sami nasarar kashi 81%, idan aka kwatanta da 24% kawai idan ba a bi ɗaya ko duka hanyoyin daidai ba.