Ikhodi Yezakhi Zofuzo Efa Lezimpawu
Ifa inqubo lapho izici zezinto eziphilayo zidluliselwa khona zisuka kubazali ziye ezinganeni zabo. Kungani ingane ingaba nombala wamehlo ofanayo noyise, umbala wezinwele ofanayo nonina, noma ngisho nokuthambekela ezimweni ezithile zempilo? Impendulo ilele kukhodi yezakhi zofuzo, "ulimi" lwezinto eziphilayo olugcinwe ku-DNA olulawula indlela izinto eziphilayo ezikhula, zithuthuke futhi zisebenze ngayo. Kungale khodi yezakhi zofuzo lapho ulwazi lwezimpawu lubhalwa, lufundwe, futhi ludluliselwe kusuka esizukulwaneni kuya kwesinye.
I-DNA njengesitolo solwazi lwezakhi zofuzo
Cishe wonke amaseli emzimbeni womuntu aqukethe i-nucleus egcina i-DNA (i-deoxyribonucleic acid). I-DNA ingafaniswa nencwadi yemiyalelo yokuphila. Isakhiwo se-DNA siyi-double helix eyakhiwe amayunithi amancane abizwa ngokuthi ama-nucleotide. I-nucleotide ngayinye iqukethe esinye sezisekelo ezine ze-nitrogen: i-adenine (A), i-thymine (T), i-cytosine (C), kanye ne-guanine (G). Ukulandelana kwalezi zisekelo ezine kuba "izinhlamvu" ezakha ulimi lwezakhi zofuzo.
Ukuhlanganiswa kwesisekelo ku-DNA kuzinzile: A pairs no-T, kanti C pairs no-G. Lo mthetho wokubambisana ubalulekile ngoba uvumela i-DNA ukuthi izikopishe ngokunembile lapho amaseli ehlukana. Inqubo yokukopisha (ukuphindaphinda) iqinisekisa ukuthi inzalo yeseli ithola imiyalelo efanayo yezakhi zofuzo ukuze kugcinwe izici eziyisisekelo.
Izakhi zofuzo, ama-allele, nama-chromosome: amaphakheji emiyalelo yefa
Ulwazi lwezakhi zofuzo alusakazwa ngokungahleliwe, kodwa luhlelwe ngamayunithi asebenzayo abizwa ngokuthi ama-gene. Ama-gene ayizingxenye ze-DNA eziqukethe imiyalelo yokwenza imikhiqizo ethile—ngokuvamile amaprotheni—abe esethonya isakhiwo kanye nomsebenzi womzimba. Amaqembu ezakhi zofuzo ahlelwe ngama-chromosome, izakhiwo ezifana nentambo ezitholakala ku-nucleus yeseli.
Abantu banama-chromosome angu-46, noma amabhangqa angu-23. Ibhangqa ngalinye lakhiwe yi-chromosome eyodwa ezuzwe kubaba kanye nenye evela kumama. Yingakho umuntu enezinhlobo "ezimbili" zama-gene amaningi. Izinguqulo ezahlukene ze-gene zibizwa ngokuthi ama-allele. Isibonelo, kwi-gene ethinta umbala wamehlo, kungaba nama-allele avame ukukhiqiza umbala omningi (amehlo amnyama) noma umbala omncane (amehlo akhanyayo).
Kusho ukuthini ikhodi yezakhi zofuzo?
Nakuba i-DNA igcina ulwazi, umzimba usadinga "ukuhumusha" lolo lwazi lube yinto ephathekayo. Yilapho umqondo wekhodi yezakhi zofuzo ungena khona. Ikhodi yezakhi zofuzo iyisethi yemithetho exhumanisa ukulandelana kwezisekelo ku-DNA (noma i-RNA) nokulandelana kwama-amino acid, izakhi zamaprotheni. Amaprotheni anesibopho sezici eziningi zezinto eziphilayo: kusukela ekwakhekeni kwezinwele nesikhumba, kuya ekusebenzeni kwe-enzyme yokugaya ukudla, kuya ekulawulweni kwama-hormone.
Uma i-gene "ivuliwe," i-DNA iguqulwa ibe yi-RNA (ribonucleic acid), ikakhulukazi i-mRNA (messenger RNA). I-mRNA ithwala umlayezo we-genetic kuma-ribosome, izimboni zamaprotheni ngaphakathi kwamaseli. Kuma-ribosome, umlayezo we-mRNA ufundwa izisekelo ezintathu ngesikhathi ngamayunithi abizwa ngokuthi ama-codon. I-codon ngayinye imelela i-amino acid ethile noma isignali ethile.
Isibonelo, i-codon AUG ku-mRNA ivame ukusebenza njenge-codon yokuqala kanye namakhodi e-amino acid methionine. Kukhona nama-stop codon, njenge-UAA, i-UAG, kanye ne-UGA, abonisa ukuphela kokwenziwa kwamaprotheni. Ngakho-ke, ukulandelana kwama-codon kunquma ukulandelana kwama-amino acid, okugcina kunquma ukuma nomsebenzi weprotheni.
Kungani ikhodi yezakhi zofuzo ibalulekile ekuzuzeni ifa lezici?
Izici ezibonakalayo zezinto eziphilayo zibizwa ngokuthi ama-phenotype, njengokuphakama, umbala wesikhumba, noma uhlobo lwegazi. Ama-phenotype akhiwa ngokusebenzisana phakathi kwe-genotype (inhlanganisela yama-allele) nendawo ezungezile. Ikhodi yezakhi zofuzo iyisixhumanisi esiyinhloko phakathi kwe-genotype ne-phenotype, njengoba inquma ukuthi yimaphi amaprotheni enziwe ngolwazi lwezakhi zofuzo.
Uma i-gene ishintsha ukulandelana kwayo okuyisisekelo—okubizwa ngokuthi i-mutation—khona-ke ama-codon angashintsha. Izinguquko ze-codon zingaba nomthelela omncane, omkhulu, noma ungabi nawo nhlobo umphumela, kuye ngohlobo lwe-mutation. Isibonelo:
1. Ukuguquka okuthule: izinguquko zesisekelo azishintshi i-amino acid ngoba ama-codon amaningana angabhala ikhodi ye-amino acid efanayo.
2. Ukuguquka kwe-Missense: ushintsho esisekelweni lukhiqiza i-amino acid ehlukile, ukuze iphrotheni ikwazi ukushintsha ukusebenza.
3. Ukuguquka okungenangqondo: ushintsho lwesisekelo ludala i-stop codon kusenesikhathi kakhulu ukuze iphrotheni inqanyulwe futhi ngokuvamile ingasebenzi.
Izinguquko kula maprotheni zingabangela ukwehluka kwezici noma zibangele izimo ezithile zofuzo.
Amaphethini efa: anamandla, aphindaphindayo, futhi ayinkimbinkimbi kakhulu
UGregor Mendel wethula umqondo wofuzo ngocwaningo lwakhe ngama-peas. Kusukela lapho, amagama athi dominant kanye ne-recessive aqala ukwaziwa. Ama-allele anamandla avame ukufihla imiphumela yama-allele anamandla ku-phenotype. Uma umuntu ene-allele eyodwa ebusayo kanye ne-allele eyodwa ebusayo, isici esibusayo ngokuvamile yiso esivelayo. Kodwa-ke, ifa kubantu livame ukuba yinkimbinkimbi kakhulu kunokumane lilawule-recessive.
Ezinye zezakhiwo zihilela:
– I-Codominance, njengasesimisweni seqembu legazi le-ABO, lapho ama-alleles A no-B angavezwa khona ukuze akhe uhlobo lwegazi i-AB.
– Ukubusa okungaphelele, lapho i-heterozygous phenotype “iphakathi” (phakathi) phakathi kwe-homozygous phenotypes ezimbili.
– Izici ze-Polygenic, okungukuthi izici ezilawulwa izakhi zofuzo eziningi ngesikhathi esisodwa, isibonelo ukuphakama, umbala wesikhumba, kanye nokuthambekela kwesisindo.
Ikhodi yezakhi zofuzo ihlala iyisisekelo sazo zonke lezi zindlela ngoba izakhi zofuzo ngasinye ekugcineni zithonya ukwakheka kwamaprotheni noma ukulawulwa kwezinqubo zezinto eziphilayo emzimbeni.
Indima yendawo ekubonakalisweni kwekhodi yezakhi zofuzo
Nakuba ikhodi yezakhi zofuzo iqukethe imiyalelo, akuzona zonke imiyalelo ezisetshenziswa njalo. Umzimba unesimiso sokulawula esinquma ukuthi yiziphi izakhi zofuzo ezisebenzayo noma ezingasebenzi nganoma yisiphi isikhathi. Isibonelo, amangqamuzana esikhumba namaseli ezinzwa abelana nge-DNA efanayo kodwa aveza izakhi zofuzo ezihlukene, okuholela emisebenzini ehlukene.
Ngaphezu kwalokho, izici zemvelo ezifana nokudla okunempilo, ukuchayeka elangeni, ukucindezeleka, kanye nendlela yokuphila kungathonya ukubonakaliswa kwezakhi zofuzo. Ucwaningo lwezinguquko ekubonakalisweni kwezakhi zofuzo ngaphandle kokushintsha ukulandelana kwe-DNA lwaziwa ngokuthi i-epigenetics. I-Epigenetics isikisela ukuthi ufuzo lwezimpawu alugcini nje ngokuphathelene "nezinhlamvu" ze-DNA, kodwa nokuthi lezo zinhlamvu "zifundwa" futhi zisetshenziswe kanjani amaseli.
Ikhodi yezakhi zofuzo kanye nempilo
Ukuqonda ikhodi yezakhi zofuzo kubalulekile ekunakekelweni kwezempilo kwanamuhla. Izifo eziningi zinezakhi zofuzo, njengezinhlobo ezithile ze-anemia, ukuphazamiseka kwe-metabolic, noma ukuthambekela kwezifo ezithile. Ngokusebenzisa ukuhlaziywa kwe-DNA, odokotela bangabona izinguquko ezingase zibangele isifo, bahlole ingozi, futhi banqume nokwelashwa okufanele kakhulu.
Intuthuko yezobuchwepheshe efana nokulandelana kwe-DNA kanye nokuthuthukiswa kokwelashwa kwezakhi zofuzo kuvule amathuba amasha okuvimbela noma ukwelapha izifo zezakhi zofuzo. Kodwa-ke, ukusetshenziswa kwalolu lwazi kuphakamisa nemibuzo yokuziphatha: indlela yokuvikela ubumfihlo bedatha yezakhi zofuzo, ukuqinisekisa ukufinyelela okulinganayo, kanye nokuvimbela ukubandlululwa okusekelwe olwazini lwezakhi zofuzo.
Isiphetho
Ikhodi yezakhi zofuzo iyisimiso esiyisisekelo esichaza indlela ulwazi oluku-DNA oluhunyushwa ngayo kumaphrotheni akha futhi alawula impilo. Ekuzuzeni izici, ikhodi yezakhi zofuzo isebenza njengendlela eyinhloko exhumanisa izakhi zofuzo ezizuzwe kubazali nezici ezibonakala ezinganeni. Ukwehluka kokulandelana kwezisekelo, inhlanganisela yama-allele, ukulawulwa kokubonakaliswa kwezakhi zofuzo, kanye nethonya lemvelo ndawonye kwakha ukuhlukahluka kwezici ezintweni eziphilayo. Ngokuqonda ikhodi yezakhi zofuzo, asiqondi nje kuphela imvelaphi yezici zomndeni kodwa futhi sithola isihluthulelo esibalulekile sokuthuthuka kwebhayoloji, ezokwelapha, kanye nokuqonda kwethu impilo ngokwayo.
