Ukuqonda ukuhlukahluka ku-Alleles
Uma ufunde ngesimo sezakhi zofuzo, kungenzeka ukuthi uhlangabezane nemigomo ethi "homozygous" noma "heterozygous"? Kodwa lisho ukuthini la magama? Futhi yiziphi imiphumela ezingokoqobo zokuthi "u-homozygous" noma "heterozygous" yegesi ethile?
Kuyini iGene ?
Ngaphambi kokuchaza i-homozygous ne-heterozygous, kufanele sicabange ngokuphathelene nezakhi zofuzo. Ngamanye amaseli akho aqukethe ama-DNA (deoxyribonucleic acid) ende kakhulu.
Lokhu kungokwakho okubonakalayo okutholakala kubazali bakho ngamunye.
I-DNA iqukethe uchungechunge lwezinto ezibizwa ngokuthi i-nucleotides. Kunezinhlobo ezine ezahlukene ze-nucleotide ku-DNA: i-adenine (A), i-guanine (G), i-cytosine (C), ne-thymine (T). Ngaphakathi kweseli, i-DNA ivame ukutholakala izikhwebu zibe ama-chromosomes (etholakala emazingeni angu-23 ahlukene).
AmaGenesis ayizigaba ezithile zeDNA ngenhloso ehlukile. Lezi zingxenye zisetshenziswa ngomunye umshini ngaphakathi kweseli ukwenza amaprotheni athile. Ama-protein yizona zakhi zokwakha ezisetshenziselwa izindima eziningi ezibucayi ngaphakathi komzimba, kubandakanya ukwesekwa kwesakhiwo, ukufaka iseli, ukumiswa kwamakhemikhali nokuthutha. Iseli lenza amaprotheni (ngaphandle kwamabhuloki okwakha, ama-amino acids) ngokufunda ukulandelana kwama-nucleotide atholakala ku-DNA. Iseli isebenzisa uhlelo lokuhumusha ukusebenzisa ulwazi ku-DNA ukwakha amaprotheni akhethekile ngezakhiwo ezithile nemisebenzi.
Izakhi zofuzo ezicacile emzimbeni zifeza izindima ezihlukile. Ngokwesibonelo, i-hemoglobin iyinkimbinkimbi yamaphrotheni eyenza ukuthwala umoya-mpilo egazini. Izakhi zofuzo ezihlukahlukene (ezitholakala ku-DNA) zisetshenziselwa iseli ukwenza izinhlaka ezithile zeprotheni ezidingekayo kule njongo.
Uzuza i-DNA yabazali bakho.
Ngokukhululekile, isigamu se-DNA yakho sivela kumama wakho, kanti enye ingxenye uvela kuyihlo. Ngezakhi zofuzo eziningi, uzuza i-copy eyodwa kumama wakho nenye evela koyihlo. (Nokho, kukhona okuhlukile okubandakanya ama-chromosomes amabili okuthiwa ama-chromosomes ocansini. Ngenxa yokuthi ama-chromosomes ocansini asebenza, abesilisa bazuza i-copy eyodwa yezakhi ezithile zofuzo.)
Izinguquko kuGenesis
Ikhodi yofuzo yabantu isifana kakhulu: Amaphesenti angama-99 ama-nucleotide ayingxenye yezakhi zofuzo afanayo kuwo wonke umuntu. Kodwa-ke, kukhona ukuhluka okuhlukile ekulandelaneni kwama-nucleotide ezigabeni ezithile. Isibonelo, ukuhlukahluka kwesinye segesi kungase kuqale ngokulandelana kwe-A T TGCT, futhi enye inguquko ingase iqale i-A C TGCT esikhundleni. Ukuhlukahluka okuhlukile kwezakhi zofuzo kuthiwa yi-alleles.
Ngezinye izikhathi lezi zinguquko azenzi umehluko emaprotheni ekugcineni, kodwa ngezinye izikhathi zenza. Kungabangela umehluko omncane kuphrotheni okwenza ukuthi usebenze ngokuhlukile.
Umuntu kuthiwa u-homozygous for gene if they have two copies of gene. Esikhathini sethu, lokhu kuzoba amakhophi amabili e-gene eqala "I- T TGCT" noma amakhophi amabili e-version eqala "I- T CCT". I-Heterozygous isho nje ukuthi umuntu unezinguqulo ezimbili ezahlukene zesakhi (esisodwa esizuzwe njengefa kusuka komzali oyedwa, omunye omunye komunye umzali).
Esikhathini sethu, i-heterozygote izoba neyodwa inguquko yesakhi esiqala "i- C TGCT" futhi enye inguquko yesakhi iqala "I- T TCT".
Ukuguquka kwezifo
Eziningi zalezi zinguquko aziyona into enkulu, futhi nje zifaka isandla ekushintsheni okuvamile komuntu. Kodwa-ke, ezinye izinguquko ezithile zingabangela izifo zabantu. Yilokho okukhulunywa ngakho ngabantu lapho bekhuluma ngokuthi "homozygous" nelithi "heterozygous": uhlobo oluthile lokuguquka okungabangela isifo.
Isibonelo esisodwa yisifo se- sickle cell anemia . E-sickle cell anemia, kukhona ukuguqulwa kwesimo se-nucleotide esisodwa esenza ushintsho ku-nucleotide yesiginja (okuthiwa i-β-globin gene).
Lokhu kubangela ushintsho olubalulekile ekuqalisweni kwe-hemoglobin. Ngenxa yalokhu, amangqamuzana abomvu ephethe i-hemoglobin aqala ukuwa phansi ngaphambi kwesikhathi. Lokhu kungaholela ezinkingeni ezifana ne-anemia nokuphefumula.
Ngokuvamile, kunamathuba amathathu ahlukene:
- Omunye u-homozygous we-β-globin gene (evamile amakhophi ajwayelekile)
- Omunye u-heterozygous (unekhophi evamile futhi engavamile)
- Omunye u-homozygous we-β-globin gene engavamile (unezimakhophi ezimbili ezingavamile)
Abantu abano-heterozygous for the gilele cell gene banekhophi eyodwa ye-gene (kusuka kumzali oyedwa) nekhophi eyodwa ethintekayo yegesi (kusuka komunye umzali). Laba bantu abatholi izimpawu ze-sickle cell anemia. Kodwa-ke, abantu abano-homozygous for the i-β-globin gene engavamile bathola izimpawu ze-sickle cell anemia.
Ingabe Ama-Heterozygotes Ahlala Athola Izifo Zomzimba?
Yebo, kodwa hhayi njalo. Kuxhomeke kuhlobo lwesifo. Kwezinye izinhlobo zezifo zofuzo , umuntu we-heterozygous cishe uzothola lesi sifo.
Ezifweni ezibangelwa yizinto ezibizwa ngokuthi izakhi zofuzo eziphezulu, umuntu udinga ikhophi elilodwa kuphela elibi lofuzo ukuba nezinkinga. Isibonelo esisodwa yisifo esiyinkinga ye- Huntington . Umuntu onesisindo esisodwa esisithintekayo (esizuzwe kumzali noma umzali) uzobe esesithola lesi sifo njenge-heterozygote. (I-homozygote ethola amakhophi amabili angavamile wesi sifo kubo bobabili abazali bayoba nesithintekayo, kodwa lokhu akuvamile kakhulu kwizifo eziphezulu zesifo.)
Kodwa-ke, ngenxa yezifo ezithathelwanayo, njenge-sickle cell anemia, i-heterozygotes ayitholi lesi sifo. (Nokho, ngezinye izikhathi bangase babe nezinye izinguquko ezicashile, kuye ngesifo.)
Kuthiwani Ngama-Chromosomes Ezocansi?
I-chromosomes yocansi yi-X ne-Y chromosomes edlala indima ekuhlukaneni ngokobulili. Abesifazane bazuza i-chromosomes ye-X, eyodwa evela kumzali ngamunye. Ngakho owesifazane angabhekwa njenge-homozygous noma heterozygous ngesici esithile kwi-X chromosome.
Amadoda adideka kancane. Bazuza ama-chromosomes amabili ehlukene ngokobulili: X no-Y. Ngoba lawa ma-chromosomes amabili ahlukile, amagama athi "homozygous" nelithi "heterozygous" awasebenzi kulezi zingu-chromosomes ezimbili kumadoda. Kungenzeka ukuthi uke wazizwa ngezifo ezixhunyaniswa ngokobulili, njenge- Duchenne muscular dystrophy . Lokhu kubonisa iphathini elihlukile lefa kunezifo ezijwayelekile noma eziqhamukayo ezizuzwe ngezinye i-chromosomes (ezibizwa nge-autosomes).
I-Heterozygote Advantage
Kwezinye izakhi zofuzo, kungenzeka ukuthi i-heterozygote inika umuntu izinzuzo ezithile. Isibonelo, kucatshangwa ukuthi ukuba i-heterozygote yegciwane le-sickle cell anemia legciwane kungase kube yisivikelo se-malaria, uma kuqhathaniswa nabantu abangenakho ikhophi engavamile.
Ifa
Ake sicabange izinguqulo ezimbili zesakhi: A kanye a. Uma abantu ababili benomntwana, kunezinto eziningana:
- Bobabili abazali bangama-AA. Zonke izingane zabo ziyoba AA kanye (homozygous for AA).
- Bobabili abazali bangama-aa. Khona-ke zonke izingane zabo ziyoba kanye (homozygous for aa).
- Omunye umzali ngu-Aa nomunye umzali ngu-Aa. Ingane yabo inamathuba angu-25 okuba yi-AA (homozygous), ithuba elingamaphesenti angu-50 lokuba i-Aa (heterozygous), kanti amaphesenti angama-25 amathuba okuba (homozygous)
- Omunye umzali ngu-Aa kanti enye ngu-aa. Ingane yabo inamathuba angu-50 okuba yi-Aa (heterozygous) kanye namaphesenti angama-50 ithuba lokuba yi-homozygous.
- Omunye umzali ngu-Aa kanti enye i-AA. Ingane yabo inamathuba angu-50 okuba yi-AA (homozygous) kanye namathuba angu-50 okuba yi-Aa (heterozygous).
Izwi elivela
Ukutadisha izakhi zofuzo kuyinkimbinkimbi. Uma isimo sezakhi zofuzo sihlala emndenini wakho, unganqikazi ukubonisana nochwepheshe wezempilo mayelana nokuthi kusho ukuthini lokhu kuwe.
> Imithombo:
> Berg JM, Tymoczko JL, Stryer L. Biochemistry. 6 th . ENew York, NY: WH Feedman neNkampani; 2007.
> Frenette PS, i-Atweh GF. Isifo se-sickle cell: ukutholakala okudala, imiqondo emisha, nesithembiso esizayo. I-Journal of Investigation Clinic . 2007; 117 (4): 850-858. i-doi: 10.1172 / JCI30920.
> Nussbaum RL, McInnes RR, uWillard HF, uHamosh A. Genetics kuMithi. Philadelphia, PA: Sauders Elsevier; 2007.