Izakhi zofuzo

I-Genetics ngukucwaninga ngofuzo, inqubo yomzali yokudlulisela izakhi zofuzo ezithile ezinganeni zakhe. Ukubukeka komuntu - ubude, umbala wezinwele, umbala wesikhumba, nombala wamehlo - kunqunywa yizakhi zofuzo. Ezinye izici ezithintwe ngofuzo yilezi:

• Amathuba okuthola izifo ezithile
• Amakhono engqondo
• Amakhono wemvelo

Isici esingajwayelekile (anomaly) esidluliselwa ngemindeni (esizuzwe njengefa) singa:

• Ungabi namthelela empilweni yakho noma enhlalakahleni yakho. Isibonelo, isici singavele sibangele isiqeshana esimhlophe sezinwele noma i-earlobe ende ende kunokujwayelekile.
• Yiba nomphumela omncane kuphela, njengobumpumputhe bombala.
• Yiba nomthelela omkhulu kwikhwalithi yakho noma kubude bempilo yakho.

Ngokuphazamiseka okuningi kofuzo, ukwelulekwa ngezakhi zofuzo kuyalulekwa. Imibhangqwana eminingi ingase ifune ukufuna ukuxilongwa ngaphambi kokubeletha uma omunye wabo enenkinga yofuzo.

Abantu banamaseli anama-chromosomes angama-46. Lezi ziqukethe ama-chromosomes ama-2 anquma ukuthi angobuphi ubulili (ama-X nama-Y chromosomes), nama-chromosomes angama-22 ama-nonsex (autosomal) chromosomes. Abesilisa bangu- "46, XY" bese abesifazane bangu- "46, XX." Ama-chromosomes akhiwa ngemicu yolwazi lofuzo olubizwa nge-DNA. I-chromosome ngayinye inezingxenye ze-DNA okuthiwa izakhi zofuzo. Izakhi zofuzo zithwala imininingwane edingwa ngumzimba wakho ukwenza amaprotheni athile.

I-chromosomes ngayinye yama-autosomal iqukethe i-chromosome eyodwa evela kumama neyodwa evela kubaba. I-chromosome ngayinye kubhangqwana iphethe imininingwane efanayo ngokuyisisekelo; okungukuthi, umbhangqwana ngamunye we-chromosome unezakhi zofuzo ezifanayo. Kwesinye isikhathi kunokuhluka okuncane kwalezi zofuzo. Lokhu kwehlukahluka kwenzeka ngaphansi kokungu-1% kokulandelana kwe-DNA. Izakhi zofuzo ezinokuhlukahluka zibizwa ngokuthi ama-alleles.

Ezinye zalezi zinguquko zingabangela isakhi sofuzo esingavamile. Isakhi esingajwayelekile singaholela kuphrotheni engajwayelekile noma inani elingajwayelekile leprotheyini ejwayelekile. Kuma-chromosomes angama-autosomal, kunamakhophi amabili wesakhi ngasinye, eyodwa evela kumzali ngamunye. Uma olunye lwalezi zofuzo lungavamile, olunye lungenza amaprotheni anele ukuze kungabi nasifo. Uma lokhu kwenzeka, isakhi esingajwayelekile sibizwa ngokuthi yi-recessive. Izakhi zofuzo ezibuyayo kuthiwa zizuzwa njengephethini ye-autosomal recessive noma ye-X. Uma amakhophi amabili esakhiweni esingajwayelekile ekhona, isifo singakhula.

Kodwa-ke, uma kudingeka kuphela isakhi sofuzo esisodwa esingajwayelekile ukukhiqiza isifo, kuholela ekuphazamisekeni okukhulu kwefa. Endabeni yokuphazamiseka okukhulu, uma ufuzo olulodwa olungavamile lutholwa ngofuzo kunina noma kubaba, ingane kungenzeka ikhombise lesi sifo.

Umuntu onesakhi sofuzo esisodwa esingajwayelekile ubizwa ngokuthi yi-heterozygous yalolo hlobo. Uma ingane ithola isakhi sofuzo esingajwayelekile esivela kubazali bobabili, ingane izokhombisa lesi sifo futhi iyoba yi-homozygous (noma i-heterozygous) yalolo hlobo.

IZINGXAKI ZOBUFAKAZI

Cishe zonke izifo zinezakhi zofuzo. Kodwa-ke, ukubaluleka kwaleyo ngxenye kuyahlukahluka. Ukuphazamiseka lapho izakhi zofuzo zidlala khona indima ebalulekile (izifo zofuzo) kungahlukaniswa njenge:

• Ukukhubazeka kohlobo olulodwa
• Izinkinga ze-Chromosomal
• Izinto eziningi

I-single-gene disorder (ebizwa nangokuthi yi-Mendelian disorder) ibangelwa ukukhubazeka kolunye uhlobo lofuzo. Ukukhubazeka kofuzo olulodwa akuvamile. Kepha njengoba kunezinkulungwane eziningi zokuphazamiseka kofuzo olulodwa, umthelela wazo ohlangene ubalulekile.

Izinkinga zofuzo olulodwa zibonakala ngokuthi zidluliselwa kanjani emindenini. Kunamaphethini ayisisekelo ayi-6 wefa elilodwa lofuzo:

• I-Autosomal ephezulu
• I-Autosomal ngokweqile
• Okuxhunywe ku-X okuphezulu
• I-X exhumeke ngokweqile
• Ifa elixhunywe ku-Y
• Ifa lomama (mitochondrial)

Umphumela obonwayo wesakhi (ukuvela kwesifo) ubizwa ngokuthi yi-phenotype.

Efaweni elibusayo le-autosomal, ukungajwayelekile noma ukungajwayelekile kuvame ukuvela kuzo zonke izizukulwane. Ngaso sonke isikhathi lapho umzali othintekile, kungaba owesilisa noma owesifazane, enengane, leyo ngane inamathuba angama-50% okuthola lesi sifo njengefa.

Abantu abanekhophi eyodwa yesifo sofuzo esibizwa ngokuthi yizithwali. Abathwali ngokuvamile abanazo izimpawu zesifo. Kepha, isakhi zofuzo singatholwa ngokuhlolwa kwe-laboratory okubucayi.

Ngefa le-autosomal recessive, abazali bomuntu othintekile kungenzeka bangakhombisi isifo (bangabathwali). Ngokwesilinganiso, ithuba lokuthi abazali abaphethe bangaba nezingane ezihlakulela lesi sifo lingama-25% ngokukhulelwa ngakunye. Izingane zesilisa nezesifazane cishe nazo zingathinteka. Ukuze ingane ibe nezimpawu zesifo se-autosomal recessive, ingane kufanele ithole isakhi esingajwayelekile kubazali bobabili. Ngoba izinkinga eziningi eziphindelelayo azivamile, ingane isengozini enkulu yesifo esiphindayo uma abazali behlobene. Abantu abahlobene nabo kungenzeka ukuthi bazuze ifa elifanayo elingavamile kukhokho oyedwa.

Kumafa aphindaphindiwe axhunywe ku-X, ithuba lokuthola lesi sifo liphezulu kakhulu kwabesilisa kunabesifazane. Njengoba uhlobo olungajwayelekile luqhutshwa ku-X (abesifazane) i-chromosome, abesilisa abaludluliseli emadodaneni abo (azokwamukela i-Y chromosome koyise). Kodwa-ke, bayayidlulisela emadodakazini abo. Kwabesifazane, ukuba khona kwe-X eyodwa ejwayelekile ye-chromosome kufihla imiphumela ye-X chromosome enofuzo olungajwayelekile. Ngakho-ke, cishe wonke amadodakazi endoda ethintekile abonakala esejwayelekile, kepha onke angabathwali bohlobo olungajwayelekile. Njalo lapho la madodakazi ezala indodana, kunamathuba angama-50% okuthi indodana ithole isakhi sofuzo esingajwayelekile.

Kwifa elibusayo elixhunywe ku-X, ufuzo olungavamile luvela kwabesifazane noma ngabe kukhona okukhona okujwayelekile kwe-X chromosome. Njengoba abesilisa bedlulisa i-Y chromosome emadodaneni abo, abesilisa abathintekayo ngeke babe nawo amadodana athintekayo. Onke amadodakazi abo azothinteka, noma kunjalo. Amadodana noma amadodakazi abesifazane abathintekile bazoba namathuba angama-50% okuthola lesi sifo.

IZIBONELO ZOKUPHILA KWAMANYE AMA-GENE

Okweqile kwe-Autosomal:

• Ukushoda kwe-ADA (kwesinye isikhathi kubizwa ngokuthi "umfana osesigubeni")
• Ukushoda kwe-Alpha-1-antitrypsin (AAT)
• ICystic fibrosis (CF)
• I-Phenylketonuria (PKU)
• I-sickle cell anemia

I-X exhunywe ngokweqile:

• I-Duchenne muscular dystrophy
• I-hemophilia A

I-Autosomal ephezulu:

• I-hypercholesterolemia ejwayelekile
• Isifo seMarfan

Okuxhunywe ku-X:

Izinkinga ezimbalwa, ezingavamile, kuphela ezixhunywe ku-X. Enye yazo ama-rickets we-hypophosphatemic, abuye abizwe nangokuthi u-vitamin D -urickets rickets.

IZINKINGA EZIQHELEKILEYO

Ezingxenyeni ze-chromosomal, isici singenxa yokweqa ngokweqile noma ukushoda kwezakhi zofuzo eziqukethwe engxenyeni ephelele ye-chromosome noma ye-chromosome.

Izinkinga ze-Chromosomal zifaka:

• Isifo se-22q11.2 microdeletion syndrome
• I-Down syndrome
• I-Klinefelter syndrome
• I-Turner syndrome

IZINGXAKI EZININGI EZININGI

Izifo eziningi ezivame kakhulu zibangelwa ukuhlangana kwezakhi zofuzo eziningana kanye nezinto ezisemvelweni (ngokwesibonelo, ukugula kumama nemithi). Lokhu kufaka phakathi:

• Isifuba Somoya
• Umdlavuza
• Isifo senhliziyo
• Isifo sikashukela
• Umfutho wegazi ophezulu
• Unhlangothi

IZINGXAKI EZIXHUMENE NE-DNA

IMitochondria yizakhiwo ezincane ezitholakala kumaseli amaningi omzimba. Babhekene nokukhiqizwa kwamandla ngaphakathi kwamaseli. IMitochondria iqukethe i-DNA yabo yangasese.

Eminyakeni yamuva nje, izinkinga eziningi zikhonjisiwe ukuthi zibangelwa ushintsho (ukuguquka) kwe-DNA ye-mitochondrial. Ngoba i-mitochondria ivela eqandeni labesifazane kuphela, izifo eziningi ezihlobene ne-DNA ezidluliselwa kumama zidluliselwa zisuka kumama.

Izinkinga ezihlobene ne-DNA yeMitochondrial zingavela noma ngasiphi isikhathi. Zinezimpawu nezimpawu ezahlukahlukene. Lezi zinkinga zingadala:

• Ubumpumputhe
• Ukubambezeleka kwentuthuko
• Izinkinga zamathumbu
• Ukulahlekelwa ukuzwa
• Izinkinga zesigqi senhliziyo
• Ukuphazamiseka komzimba
• Isiqu esifushane

Ezinye izifo zaziwa nangokuthi iziphazamiso ze-mitochondrial, kepha azibandakanyi ukuguqulwa kwe-DNA ye-mitochondrial. Lezi zinkinga zivame ukukhubazeka kofuzo olulodwa. Balandela iphethini efanayo yefa njengezinye izifo zofuzo ezilodwa. Iningi liyi-autosomal eyeqile.

Homozygous; Ifa; Heterozygous; Amaphethini wefa; Ufuzo nezifo; Kuzuzisa; Izimpawu zofuzo

• Izakhi zofuzo

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I-Korf BR. Izimiso zofuzo. Ku: IGoldman L, iSchafer AI, ama-eds. Imithi yeGoldman-Cecil. Umhla ka-26. IPhiladelphia, PA: Elsevier; 2020: isahluko 35.

UScott DA, uLee B. Indlela yofuzo kwezokwelapha izingane. Ku: Kliegman RM, St Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Incwadi kaNelson Yezingane. Umhlaka 21. IPhiladelphia, PA: Elsevier; 2020: isahluko 95.