Tlhophiso ea Genome Liseleng tsa Eukaryotic
Li-genome tsa lisele tsa eukaryotic—tse kang tsa liphoofolo, limela, li-fungus le li-protist—li na le boemo bo rarahaneng le bo hlophisitsoeng hantle ba tlhophiso. Ho fapana le li-prokaryotes, tseo ka kakaretso li nang le DNA e chitja e fumanehang sebakeng se le seng (nucleoid), lisele tsa eukaryotic li boloka boholo ba lintho tsa tsona tsa lefutso ka har'a nucleus ka mokhoa oa li-chromosome tse otlolohileng. Ho lekana DNA e telele ka har'a nucleus e nyane ha e ntse e le bonolo ho e fumana bakeng sa tlhahiso ea liphatsa tsa lefutso le ho ikatisa, lisele tsa eukaryotic li thehile sistimi e sebetsang hantle le e matla ea ho paka DNA. Tlhophiso ena ea liphatsa tsa lefutso ha se taba feela ea "poloko," empa hape ke ea "ho laola" hore na liphatsa tsa lefutso li sebetsa neng le hokae.
1. Likarolo tse ka Sehloohong tsa Genome ea Eukaryotic
Genome ea eukaryotic e entsoe ka DNA e arotsoeng ka li-chromosome tse 'maloa. Palo ea li-chromosome e fapana ho ea ka mefuta; batho ba na le li-chromosome tse 46 (lipara tse 23), raese e na le tse 24, 'me limela tse ling li ka ba le makholo. Ntle le genome ea nyutlelie, li-eukaryote li boetse li na le DNA ka har'a li-organelle tse kang mitochondria (hoo e batlang e le li-eukaryote tsohle) le li-chloroplast (limeleng le boleleng). DNA ka har'a li-organelle tsena hangata e nyane 'me e na le liphatsa tsa lefutso tsa bohlokoa tse amanang le ho hema ha sele kapa photosynthesis.
Ka hara genome ya nyutlelia, ho na le dijini tse ngolang diprotheine, dijini tse ngolang di-RNA (mohlala, rRNA, tRNA, miRNA), le dibaka tse sa ngolang di-coding, hangata di le ngata haholo ka palo ho feta dibaka tse ngolang diprotheine. Dibaka tse sa ngolang di-coding ha se hore ha di "na thuso"; tse ngata tsa tsona di sebetsa e le dikarolo tsa taolo tse kang di-promoter, di-enhancer, di-silencer, le di-insulator tse laolang hore na dijini di sebetsa neng.
2. Ho paka DNA: Ho tloha ho DNA ea Helix e habeli ho ea ho li-chromosome
Bolelele ba DNA ea eukaryotic bo makatsa: haeba DNA e ka har'a sele e le 'ngoe ea motho e ne e ka atolosoa, e ne e tla fihla bolelele ba limithara tse ka bang peli, leha khubu ea sele e le bophara ba li-micrometer tse 'maloa feela. Phephetso ena e hlōloa ka ho paka ka mekhahlelo e mengata ho sebelisoa liprotheine tsa histone le liprotheine tse ling tsa sebopeho.
a. Nucleosome: Yuniti ya Motheo ya Chromatin
Boemo ba motheo ka ho fetisisa ba ho paka ke nucleosome, e leng DNA e phuthetsoeng ho potoloha motsoako oa liprotheine tse robeli tsa histone (histone octamer). Lipara tse ka bang 147 tsa motheo tsa DNA li phuthela li-histone, li etsa sebopeho sa "li-bead-on-a-string". Pakeng tsa li-nucleosome ho na le likhoele tsa DNA tse hokahaneng tsa bolelele bo fapaneng, hangata li tsitsisoa ke histone H1.
b. Lifaeba tsa Chromatin le Maemo a Tsoetseng Pele a ho Paka
Li-nucleosome ha li eme sebopehong sa "li-beaded"; li ka sebelisana 'me tsa etsa li-fiber tse teteaneng. Ka tloaelo, tsena hangata li bitsoa li-fiber tsa 30-nm, leha lintlha tsa meaho ena liseleng tse phelang li fetoha haholo 'me ha se kamehla li tšoanang. Ho feta moo, li-fiber tsa chromatin li etsa li-loops tse khomaretsoeng moralo oa protheine ea nyutlelie, ka hona li hlophisa DNA ka sebaka.
c. Li-chromosome tsa Metaphase
Nakong ea karohano ea sele (mitosis le meiosis), chromatin e ikamahanya ka thata ho etsa li-chromosome tsa metaphase, tse bonahalang habonolo tlas'a microscope. Ho ikamahanya hona hoa bohlokoa bakeng sa ho arola DNA ka nepo ho lisele tsa morali ntle le ho hohlana kapa ho robeha.
3. Chromatin: Euchromatin le Heterochromatin
Mokhatlo oa liphatsa tsa lefutso o boetse o amana le kamoo DNA e "buloang" kapa e "koetsoeng" kateng hore e fumanehe ke mechini ea ho ngola.
– Euchromatin ke mofuta o hlephileng oa chromatin, o nang le liphatsa tsa lefutso tse ngata tse sebetsang, 'me o ngoloa habonolo. Sebaka sena se atisa ho "buleha" haholoanyane, se lumellang lintho tse etsang hore ho ngoloe le RNA polymerase ho tlamahana le DNA.
– Heterochromatin ke mofuta o monyane haholoanyane oa chromatin, ka kakaretso o nang le ts'ebetso e tlase ea ho ngola. Heterochromatin e ka ba e kopanyang (kamehla e monyane, mohlala, ho centromeres le telomeres) kapa ea facultative (e ka fapana ho latela mofuta oa sele kapa mohato oa nts'etsopele, mohlala, chromosome ea X e sa sebetseng ho liphoofolo tse anyesang tse tšehali).
Phapang ena e bonts'a hore sephutheloana sa DNA ha se sa 'mele feela, empa hape ke mokhoa oa taolo ea liphatsa tsa lefutso.
4. Likarolo tsa Sebopeho sa Li-Chromosome: Li-Centromere, Li-Telomere, le Tšimoloho ea ho Ikatisa
Chromosome e 'ngoe le e 'ngoe ea eukaryotic e na le likarolo tsa bohlokoa tse netefatsang botsitso ba liphatsa tsa lefutso le lefa:
– Sentromere ke sebaka seo kinetochores e thehoang ho sona, e leng dibopeho tsa protheine tse hokahanyang di-chromosome le difaeba tsa spindle nakong ya karohano ya sele. Sentromere e bohlokwa bakeng sa karohano e nepahetseng ya di-chromatids tsa kgaitsedi.
– Li-Telomere ke lipheletso tsa li-chromosome, tse entsoeng ka ho pheta-pheta ha DNA le liprotheine tse sireletsang. Li-Telomere li thibela lipheletso tsa li-chromosome hore li se ke tsa nkoa e le DNA e senyehileng 'me li thibela ho kopana pakeng tsa li-chromosome. Ho khutsufala ha li-telomere ho etsahala nakong ea ho ikatisa ha DNA, 'me enzyme telomerase e ka li lelefatsa liseleng tse itseng.
– Tšimoloho ea ho ikatisa (ori) ke moo ho qaloang teng ha ho ikatisa ha DNA. Ho li-eukaryote, ho na le li-ori tse ngata ho chromosome e le 'ngoe, e leng se lumellang ho ikatisa ho etsahala kapele le ka katleho.
5. Meralo ea 3D ea Genome ka har'a Nucleus
Diphuputso tsa sejwalejwale di bontsha hore genome ha e a hlophiswa ka tsela e sa reroang ka hara nucleus ya sele. DNA e beilwe sebakeng sa mahlakore a mararo, e leng se susumetsang tlhahiso ya jini.
a. Sebaka sa Chromosome
Chromosome ka 'ngoe e na le tšekamelo ea ho lula sebakeng se itseng ka har'a khubu e bitsoang sebaka sa chromosome. Leha ho na le likamano lipakeng tsa li-chromosome, karohano ea sebaka e thusa ho boloka taolo le ho fokotsa ho ts'oaroa.
b. Ho seha le ho ikopanya hole
Liphatsa tsa lefutso li ka kenngoa tšebetsong ke li-enhancer tse hole ka mola empa li le haufi ka sebaka ka lebaka la ho thehoa ha li-loop tsa chromatin. Liprotheine tse kang CTCF le cohesin complex li bapala karolo e kholo ho theheng le ho bolokeng li-loop tsena.
c. TAD (Mafapha a Amanang le Maemo a Thuto)
Genome e boetse e arotsoe ka libaka tsa tšebelisano tse bitsoang li-TAD, libaka tsa DNA tse sebelisanang khafetsa le tsona ho feta libaka tse ling. Li-TAD li thusa ho netefatsa hore li-enhancer li kenya tšebetsong liphatsa tsa lefutso tse "nepahetseng" le ho thibela tse sa batleheng ho sebetsa.
6. Epigenetics: Ho Laola Liphatsa tsa Lefutso Ntle le ho Fetola Tatellano ea DNA
Tlhophiso ea li-genome tsa eukaryotic e susumetsoa haholo ke mekhoa ea epigenetic, e leng liphetoho tse amang tlhahiso ea li-gene ntle le ho fetola tatellano ea motheo oa DNA. Mekhoa e 'meli e meholo ke:
– Liphetoho tsa Histone, tse kang acetylation, methylation, phosphorylation, le ubiquitination. Histone acetylation ka kakaretso e etsa hore chromatin e bulehe haholoanyane mme e eketsa phetolelo, athe mefuta e meng ea methylation e ka kenya tshebetsong kapa ya thibela phetolelo ho latela sebaka sa masalla.
– Metsi a DNA, ao hangata a hlahang ho li-cytosine maemong a CpG liphoofolong. Metsi a DNA hangata a amahanngoa le ho hatelloa ha transcriptional le ho thehoa ha heterochromatin.
Epigenetics e dumella genome e tshwanang ho hlahisa mefuta e fapaneng ya disele tse nang le mesebetsi e fapaneng, jwalo ka disele tsa methapo, disele tsa mesifa le disele tsa madi, ka dipaterone tse fapaneng tsa tlhahiso ya dijini.
7. Li-genome tsa Organelle: Mitochondria le Chloroplasts
Ntle le genome ea nyutlelie, li-eukaryote li na le genome ea mitochondrial, 'me limela, li na le li-chloroplast. Li-genome tsa organella hangata li chitja 'me li futsitsoe ke bo-'mè mefuteng e mengata. Le hoja palo ea liphatsa tsa lefutso mitochondria e le nyane haholo, mosebetsi oa tsona ke oa bohlokoa bakeng sa tlhahiso ea matla. Hoa thahasellisa hore liphatsa tsa lefutso tse ngata tse neng li fumanoa li-organelle tsena li falletse khubung nakong ea phetoho, kahoo mosebetsi oa organelle hangata o itšetlehile ka liprotheine tse kentsoeng ke genome ea nyutlelie.
8. Litlamorao tsa Mokhatlo oa Genome bakeng sa Bophelo bo Botle le Tsoelo-pele
Tlhophiso e nepahetseng ea genome e netefatsa botsitso ba liphatsa tsa lefutso. Tšenyo ea telomere, liphoso tsa ho thehoa ha chromatin, kapa tšitiso ea taolo ea epigenetic li ka baka mafu a fapaneng, ho kenyeletsoa kankere le mathata a nts'etsopele. Mohlala, liphetoho mekhoeng ea methylation ea DNA li ka kenya tšebetsong li-oncogene kapa tsa tima liphatsa tsa lefutso tse hatellang hlahala. Ho feta moo, liphetoho sebopehong sa chromosome, joalo ka translocations, li ka kopanya liphatsa tsa lefutso tse peli, tse fellang ka liprotheine tse kotsi tsa fusion.
Thutong ea ho iphetola ha lintho, ho hlophisoa ha liphatsa tsa lefutso ho lumella phetoho: ho pheta-pheta ha liphatsa tsa lefutso, ho kopanya hape, le liphetoho likarolong tse laolang li ka hlahisa mesebetsi e mecha ntle le ho fetola tsamaiso eohle. Kahoo, ho rarahana ha eukaryotic ho hlaha haholo-holo ka lebaka la bokhoni ba ho laola ka nepo tlhahiso ea liphatsa tsa lefutso ka mokhatlo oa liphatsa tsa lefutso tse nang le mekhahlelo e mengata.
Qetello
Tlhophiso ea liphatsa tsa lefutso liseleng tsa eukaryotic ke sistimi e hlophisitsoeng hantle le e matla, ho tloha ho li-nucleosome e le yuniti ea motheo, ka ho thehoa ha euchromatin le heterochromatin, ho ea ho meralo ea mahlakore a mararo joalo ka libaka tsa chromosome le li-TAD. Maemo ana kaofela a tlhophiso a bapala karolo ea bohlokoa ho netefatseng hore DNA e kopantsoe, e sirelelitsoe, e phetoa, e futsitsoe, 'me e hlahisoa ho latela litlhoko tsa sele. Ka mekhoa ea epigenetic le taolo ea sebaka ka har'a nucleus, lisele tsa eukaryotic li khona ho laola liphatsa tsa lefutso tse makholo ho isa ho tse likete ka nepo. Ho utloisisa tlhophiso ea liphatsa tsa lefutso ha ho bohlokoa feela bakeng sa baeloji ea motheo empa hape ke senotlolo sa ho utloisisa maloetse, botsofali le boqapi ba theknoloji ea baeloji nakong e tlang.
