Vana vakaberekwa kubva pamuviri vane pamuviri vanonzi mapatya kana mapatya (katatu). Uye kune nzira mbiri dzekukura kwekudzivirira nemapatya: dizygotic (twese-twided) twins uye mapatya akafanana.
Ndeupi musiyano pakati pemapatya nemapatya?
Mumakumbo maviri-jawed twins, mukadzi anokura pamwe chete maviri kana kupfuura ova mune rimwe kana mavari mavari, ayo akazobudirira. Dzimwe nguva nguva yekudyara kwavo yakasiyana nemaawa akawanda kana kunyange mazuva. Vana vakaberekwa vanogona kuita zvepabonde zvakafanana kana kuti vanove vakasiyana zvepabonde. Mukuita kudaro, vane mumwe nomumwe wavo wega chromosomes, saka kazhinji havataridzi zvakaenzana, kunyange zvazvo kumwe kufanana hakuna mubvunzo kuonekwa.
Ne monozygotic (odnoyaytsevymi) mapatya, mamiriro acho ndeaya anotevera: zhi rimwe rinosungirwa nemumwe spermatozoon. Mushure meizvozvo, zygote yakakamurwa kuva maviri emadzimai akasiyana, ayo anokura uye anokura kuva vana vaviri vanoyevedza. Panguva imwe chete sechikonzero chekuzvitakura uku, vakomana vanowanzoberekwa, izvo zvinowanikwa zvipi zvayo.
Zvinetso zvekusimbiswa kwamababa (mapatya)
Pakati pezvimwe zvinetso zvematambudziko akawanda ekudzivirira pamuviri ndiko kuparadzaniswa kwekuita mababa. Kuparadzaniswa mapatya kunonoka mukukura kweimwe yezvibereko. Ndiko kuti, mumwe wevana anowedzera zviri nani, achidzivisa wechipiri. Chinhu chinonyanya kutyisa ndechokuti rimwe-twende twakaita neine placenta inodyana. Munyaya iyi, hupenyu hwevana vaviri huri pangozi.
Imwe mhando yezvinetso zvinonzi mapatya eSiamese. Rudzi rwemapatya aya akafanana mapatya, akabatana nemumwe. Chikonzero chechiitiko ichi mukusatidzika kuparadzaniswa kwe zygote mu 2 mafomu akazvimirira. Nenzira yakanaka, ichi chiitiko chinowanikwa munyaya imwechete kunze kwemamiriyoni gumi.