Isakhiwo se-Chromosome ezintweni eziphilayo
Ama-chromosome angenye yezingxenye ezibaluleke kakhulu emangqamuzaneni aphilayo ngoba asebenza "njengesitsha" esiyinhloko solwazi lwezakhi zofuzo. Ama-chromosome aqukethe i-DNA, equkethe izakhi zofuzo ezilawula izici, imisebenzi yomzimba, kanye nokuthuthukiswa kwesidalwa esiphilayo kusuka kuseli elilodwa kuya kumuntu ophelele. Isakhiwo sama-chromosome asimangazi nje kuphela ngesimo sawo kodwa nangendlela ahlanganiswe ngayo, ahlelwe ngayo, futhi azuzwe njengefa. Ukuqonda isakhiwo sama-chromosome kusisiza ukuchaza izenzakalo eziningi zebhayoloji, kusukela ekuzuzeni izici nokukhula kuya ezifweni zezakhi zofuzo.
Ukuqonda ama-chromosome kanye nendima yawo
Ngokuvamile, ama-chromosome ayizakhiwo ezifana nentambo ezitholakala kuyi-nucleus yeseli (ezintweni eziphilayo ze-eukaryotic), ezakhiwe yi-DNA kanye neprotheni. Ezintweni eziphilayo ze-prokaryotic ezifana namabhaktheriya, izinto zofuzo azikho ngaphakathi kwi-nucleus yeseli kodwa kunalokho zihlelwe ngesimo se-chromosome eyodwa noma izakhi eziningana ze-DNA eziyindilinga.
Imisebenzi eyinhloko yama-chromosome yile:
1. Igcina ulwazi lwezakhi zofuzo ngendlela yokulandelana kwe-DNA.
2. Ilawula ukuvezwa kwezakhi zofuzo, okungukuthi lapho izakhi zofuzo zisebenza noma zingasebenzi.
3. Kuqinisekisa ukusatshalaliswa okufanele kwezinto zofuzo lapho amangqamuzana ehlukana (i-mitosis kanye ne-meiosis).
4. Ukudlulisela izimfanelo ezivela kubazali ezinganeni zabo.
Ngamanye amazwi, ama-chromosome angacatshangwa njengohlelo oluhlelekile kakhulu lokufaka nokuphatha ulwazi lwezinto eziphilayo.
Izingxenye ze-Chromosome: i-DNA neprotheni
Ama-chromosome akhiwe yizinhlanganisela ze-DNA namaprotheni, ikakhulukazi amaprotheni e-histone. I-DNA iyi-molecule ende equkethe ulwazi lwezakhi zofuzo ngokulandelana kwezisekelo ze-nitrogen (A, T, G, C). Kodwa-ke, i-DNA ende kangaka ayinakushiywa nje "ku-nucleus encane yeseli. Ngakho-ke, i-DNA kumele ipakishwe kahle.
Yilapho indima yama-histone iba yinto ebalulekile khona. Amaprotheni e-histone asebenza njenge-"spools" lapho i-DNA iboshwe khona. Le nhlanganisela ye-DNA namaprotheni ibizwa ngokuthi i-chromatin. Isakhiwo se-chromatin siyashintshashintsha: ngaphansi kwezimo ezithile, kukhululekile ukuvumela ukubhalwa kwezakhi zofuzo, kanti ngaphansi kwezinye izimo, kuncane kakhulu ukuvikela i-DNA nokwenza kube lula ukuhlukaniswa kwama-chromosome ngesikhathi sokuhlukaniswa kwamaseli.
Izinga lokupakishwa kwe-DNA kuma-chromosome
Isakhiwo se-chromosome akuyona nje "intambo yentambo," kodwa kunalokho umphumela wenqubo yokufaka i-DNA enezinyathelo eziningi. Ngamafuphi, izigaba zokufaka zifaka:
1. I-DNA double helix
I-DNA iyi-double helix enobubanzi obungaba ngu-2 nm. Lesi yisimo esiyisisekelo se-DNA.
2. I-Nucleosome
I-DNA izungezwe inhlanganisela yamaprotheni ayisishiyagalombili e-histone ukuze yakhe iyunithi ebizwa ngokuthi i-nucleosome. Isimo sayo sivame ukufaniswa “nama-beads entanjeni.” Ama-nucleosome abalulekile ekuhlanganisweni kokuqala kwe-DNA.
3. I-Chromatin fiber
Ama-nucleosome abe esehlangana ndawonye ngokuqinile, akha imicu ye-chromatin ejiyile. Lokhu kuhlanganiswa kwandisa ubuningi be-DNA ukuze ilingane ngaphakathi kwe-nucleus yeseli.
4. Ama-Chromatin loops kanye nama-domain
Imicu ye-Chromatin yakha izakhiwo ezigoqekile ezinamathele ohlakeni lwephrotheni ku-nucleus. Ukuhlelwa kwalezi zigoqo kuthonya kakhulu ukufinyelela kwezakhi zofuzo, ngakho-ke, kuhlotshaniswa nokulawulwa kokubonakaliswa kwezakhi zofuzo.
5. Ama-chromosome afinyeziwe
Uma iseli selizohlukana, i-chromatin iqina ngokuqinile ukuze yakhe ama-chromosome, abonakala ngokucacile ngaphansi kwe-microscope ekhanyayo. Lesi yisimo "X" esivame ukusibona ezincwadini zebhayoloji, yize sibonakala kakhulu ngesikhathi sesigaba se-metaphase sokuhlukaniswa kwamaseli.
Lokhu kuhlanganiswa kwamazinga amaningi kukhombisa ukuthi ukwakheka kwama-chromosome akuyona nje indaba yesimo, kodwa futhi kuyindlela yokuphilayo yokulawula ukusebenza kwe-DNA.
Izingxenye eziyinhloko zama-chromosome
Ama-chromosome abonakala ngokucacile ngesikhathi sokuhlukaniswa kwamaseli anezingxenye eziningana ezibalulekile:
1. Ama-chromatids angodadewabo
Ngemva kokuphindaphinda kwe-DNA, i-chromosome iqukethe amakhophi amabili afanayo abizwa ngokuthi ama-chromatids angodadewabo. Lawa ma-chromatids amabili ahlukaniswa ngesikhathi sokuhlukaniswa kweseli ukuze iseli ngalinye lendodakazi lithole ikhophi efanayo ye-DNA.
2. Isikhungo se-Centromere
I-centromere yingxenye encane exhumanisa ama-chromatids angodadewabo. Le ndawo yakha isakhiwo sephrotheni esibizwa ngokuthi i-kinetochore, lapho imicu ye-spindle inamathela khona ngesikhathi sokuhlukaniswa kwamaseli. Indawo ye-centromere nayo inquma ukuma kwe-chromosome.
3. Ingalo p kanye no-q
Ama-chromosome anezingalo ezimbili: ingalo emfushane ibizwa ngokuthi i-p (petit) kanti ingalo ende ibizwa ngokuthi i-q. Lokhu kuhlukaniswa kuyasiza ekuhleleni izakhi zofuzo nasekuboneni ukungalingani kwe-chromosome.
4. Ama-Telomere
Ama-Telomere “ayizivalo” emaphethelweni ama-chromosome akhiwe ngokulandelana kwe-DNA okuphindaphindiwe. Umsebenzi wawo ukuvikela amaphethelo ama-chromosome ekulimaleni nokuvimbela i-DNA ekuphathweni njengezingcezu ezidinga ukulungiswa. Ama-Telomere adlala indima ekugugeni kwamaseli kanye nokuzinza kwe-genome.
5. I-Chromatin: i-euchromatin kanye ne-heterochromatin
– I-Euchromatin ikhululekile, icebile ngamajini asebenzayo, futhi ikopishwa kalula.
– I-Heterochromatin inzima kakhulu, ngokuvamile izakhi zofuzo azisebenzi kakhulu, futhi idlala indima ebalulekile ekuzinzeni kwesakhiwo se-chromosome.
Ukwehluka kwesimo se-chromosome ngokusekelwe endaweni ye-centromere
Indawo ye-centromere ithinta ukuma kwe-chromosome. Ngokuvamile, kunezinhlobo eziningana:
– I-Metacentric: i-centromere ephakathi nendawo, izingalo zombili zicishe zifane ngobude.
– I-Submetacentric: i-centromere ishintshiwe kancane, izingalo azilingani ngobude.
– I-Acrocentric: i-centromere eduze kokuphela, ingalo eyodwa imfushane kakhulu.
– I-Telocentric: i-centromere ekugcineni (ivame kakhulu kwezinye izilwane, ayivamile kubantu abavamile).
Lokhu kuhlukaniswa kubalulekile ezifundweni ze-cytogenetic, ikakhulukazi ekutholeni izinguquko zesakhiwo njengokudluliselwa noma ukususwa.
Ama-chromosome kubantu nakwezinye izinto eziphilayo
Uhlobo ngalunye lunenombolo ye-chromosome ehlukile. Abantu banama-chromosome angu-46 kumaseli omzimba (2n), aqukethe ama-autosome angu-22 kanye ne-chromosome eyodwa yobulili (XX noma XY). Ama-Gametes (isidoda namaseli eqanda) anengxenye yalelo nani, ama-chromosome angu-23 (n), ngenxa ye-meiosis.
Inani lama-chromosome alihlali lihambisana ngqo "nezinga lobunzima" bento ephilayo. Ezinye izitshalo zinama-chromosome amaningi kakhulu kunabantu. Lokhu kungase kube ngenxa ye-polyploidy (ukuphindaphindwa kwamasethi ama-chromosome), okuyinto evamile ezitshalweni futhi enegalelo ekuhlukeni kwezinhlobo kanye nokuvela kwazo.
Kuma-bacteria, ama-chromosome ngokuvamile ayi-molecule eyodwa ye-DNA eyindilinga. Nakuba elula, ama-bacteria asenayo i-DNA ehlanganiswe namaprotheni athile kanye nezindlela eziqinisekisa ukuphindaphindeka okufanele kanye nofuzo.
Izinguquko esakhiweni sama-chromosome kanye nomthelela wazo
Isakhiwo se-chromosome singaba nezinguquko eziholela ekushintsheni kwezakhi zofuzo noma ekungajwayelekile. Ezinye izinguquko ezivame ukufundwa zifaka:
– Ukususwa: ukulahlekelwa kwengxenye ye-chromosome.
– Ukuphindaphinda: ukuphindaphinda kwezingxenye ze-chromosome.
– Ukuguqulwa: izingxenye ze-chromosome zibuyiselwa emuva.
– Ukudluliselwa: ingxenye ithuthela kwenye i-chromosome.
Lezi zinguquko zingaba zincane, zingathathi hlangothi, noma zibe zimbi kakhulu, kuye ngezigaba ezihilelekile. Kubantu, ukungajwayelekile kwe-chromosome kungabandakanya nezinguquko enanini (isb., i-trisomy), kodwa lezi zinguquko enanini zihlobene kakhulu nokuhlukaniswa kwama-chromosome ngesikhathi se-meiosis, kunokuba zibe yisakhiwo sazo somzimba.
I-Penutup
Isakhiwo sama-chromosome ezintweni eziphilayo sibonisa ubuhlakani bezinhlelo zokugcina ulwazi lwezinto eziphilayo. Kusukela ku-DNA helix encane kuya kuma-chromosome ahlanganisiwe abonakala ngesikhathi sokuhlukaniswa kwamaseli, konke kuhlelwe ngendlela ehlelekile nehlelekile. Ama-chromosome awavikeli nje kuphela i-DNA kodwa futhi alawula ukusetshenziswa kwezakhi zofuzo futhi aqinisekise ufuzo olufanele lolwazi lwezakhi zofuzo. Ukuqonda isakhiwo sama-chromosome kuvula indlela yokuqonda izindlela eziyisisekelo zokuphila, kuyilapho kusiza ezokwelapha kanye ne-biotechnology ekutholeni nasekwelapheni izifo ezahlukahlukene zezakhi zofuzo.
Uma ungathanda, ngingangeza ingxenye encane enikezelwe ngomehluko wama-chromosome kuma-prokaryotes vs ama-eukaryotes, noma ngenze inguqulo yesihloko egxile kakhulu kuma-chromosome abantu kanye nokukhubazeka kwama-chromosome.
