Inzala

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Ngokwe-biology, inzala sisiqhamo sokwanda kwesidalwa esiphefumlayo siqhanyiswa sesinye okanye, xakusenzeka i-sexual reproduction,  abazali ababini.  Ingqokolela yenzalo isenokwaziwa njenge-brood okanye i-progeny ngokwesiqhelo. Oku kunokubhekisa kwingqokolela yesizalo esivela ngaxeshanye, esifana namantshontso enkukhu aqanduselweyo kwingqokolela enye yamaqanda, okanye kuzo zonke kuyo yonke inzalo njengakubusi beenyosi.  

Inzalo yabantu (isizukulwana) babizwa ngokuba  ngabantwana (kungajingwanga minyaka yabydala,  kusenokuthiwa kumzali womntwana omncinci, okanye ''abantwana abadala" okanye  "iimveku" okanye "abantwana abaselula"); abantwana abangamakhwenkwe ngoonyana baze abangamantombazana bona babeziintombi (jonga kwii-kinship and descent). Inzalo isenokwenzeka emva kokuba abazali bobabini bethe badibana okanye emva kokuba kwenzeke i- artificial insemination.

Inzalo yomntu ngamnye inamalungu kwaneempawu zokuzala ezininzi, ezenza okokuba zicace gca futhi zingathandabuzeki izinto ezakhiwe ngazo, nengcagciso ngazo. Njengoko isizalo sohlobo olutsha lwesidalwa esiphilayo,  sikwabizwa ngokuba ngumntwana okanye yi-sisizukulwana se-f1, sisenziwa zii-genes zikanina noyise, nabakwaziwa ngokuba sisizukulwana esingabazali. [1] Isizukulwana ngasinye kwezi sinenqwaba yee-genes nezinophawu ngomsebebzi ngamnye nangeempawu zazo.  Iinkunzi neemazi zombini zinenkxaso elinganayo kwii-genotypes zabantwa bazo abaziziqhamo zokudibana kwabo, apho ii-gametes zidi zidibane zimanyane kuze kubekho into eyenzekayo. umba obaluleke kakhulu ekwenzekeni kwesizalo somzali yi-chromosome, nesisakhiwo se-DNA esinee-genes ezininzi.[2]

Ukuqwalasela ngakumbi kwisizalo nasekubeni senzeka njani na  isizalo sesizukulwana se-f1, lufuzo olubizwa ngokuba yi- sex-linkage,[3] nekuyi-gene ebuthume phaya kwi-sex chromosome kwaye izakhiwo zolu fuzo zahlukile kwinkunzi nakwimazi. Inkcazo ebonisa itheori ye-offspring inee-genes kwizizukulwana macala omabaini abazali, iye yafezekiswa ngenkqubo ebizwa ngokuba yi-crossing-over, apho ke kuthathwa ii-genes kwii-chromosomes zenkunzi nee-genes kwii-chromosomes zethokazi, ize ke isiqhamo saloo nto ibe yinkqubo ye-meiosis ethi yenzeke, loo nto ikhokhelela ekubeni ziqhekeke kubini ke ii-chromosomes ngokulinganayo. [4] Kuyakuthi ke kusakubonakala okokuba ziziphi ii-genes ezizingqonyela ngobukho kwi-chromosomes kucace isini saloo nto izakuzalwa. Ithokazi liyakukhupha i-chromosome engu-X, ngeli lixa yona inkunzi isenokukhupha i-chromosome engu-X okanye engu-Y. Ukuba kuye kwazalwa inkunzi, i-gene iyakuba nee-chromosomes ezingu-X no-Y. Ukuba ii-chromosomes zibe ngoo-X zombini, kuyakuzalwa ithokazi.[5]

I-Cloning kukuzalwa kwe-offspring emele ii-genes ezifana nqwa nomzali wazo.  Inzala ye-cloning iqala ngokususwa kwe-nucleus eqandeni, nekuyeyona nto ilawula ubuni bee-genes.[6] Ukuze kwenzeke inkqubo ye-clone kwi-organ, kwenzeka isiqu se-cell  ze sisetyenziselwe ukuba zi-clon-e loo organ.[7] Impazamo  exhaphakileyo kwinkqubo ye-cloning yeyokuba kuzalwa kuyo isidalwa esifana nqwa nomzali lowo kwenzeke kuye le nkqubo ye-cloned. I-Cloning ikopa ii-DNA/genes zomzali ize ke ngoko yenze iikopi ze-genes ezo. I-clone ayinakuba ngumceph'ucandiwe njengoko isayakukhula kwiindawo ngeendawo ezijikeleze i-clone kwaye esenokufumana amathuba ngamathuba kwakunye namava.   Nangona uninzi lwazo zii-positive, i-cloning isoloko ijongene nemingeni ngokwee-ethics nangokwempilo yoluntu. 

Nangona ukwahlulwa-hlulwa kwe-cell nokuphindwa-phindwa kwe-DNA izezona zinto zidlala indima enkulu empilweni yomntu, maninzi amanyathelo abandakanyekayo anjengee-enzymes nee-proteins. Oko kuthetha okokuba ziininzi iimpazamo, neengxaki ezisenokwenzeka, nezibizwa ngokuba zii-mutations. I-mutation lulo naluphi na utshintsho olusisigxina kwi-organism ye-DNA kwaye olo tshintsho lukwi-offspring ye-DNA.[8] Ezinye ii-mutations zingazezilungileyo kuba zivela kumaxesha e-random evolution nezisenokulungela ezinye iintlobo,  kodwa uninzi lwee-mutations zimbi njengoko zisenokutshintsha ii-genotypes zenzala, nokunokuthi kwenze utshintsho olunokungoza ezinye iintlobo zendalo.

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Nanga amanye amaphepha ekusekelezelwe kulo olu lwazi. [tshintsha | edit source]