Kurongeka kweGenome muEukaryotic Cells
Ma genome emasero eukaryotic—akadai seemhuka, zvirimwa, fungi, uye ma protists—ane hurongwa hwakaoma uye hwakarongeka. Kusiyana nema prokaryotes, ayo anowanzova neDNA yakatenderera iri munzvimbo imwe chete (nucleoid), masero eukaryotic anochengeta akawanda ezviwanikwa zvawo zvemajini mukati menucleus muchimiro chema chromosomes akatsetseka. Kuti DNA refu ikwane mukati menucleus diki uku ichiramba iri nyore kuwana kuti majini ataure uye adzokororwe, masero eukaryotic akagadzira sisitimu yekurongedza DNA inoshanda uye ine simba. Kurongeka uku kwemajini hakusi nyaya yekungo "chengeta," asiwo "kutonga" kuti majini anoshanda riini uye kupi.
1. Zvikamu Zvikuru zveEukaryotic Genome
Genome reEukaryotic rinoumbwa neDNA rakakamurwa kuita machromosome akati wandei. Huwandu hwemachromosome hunosiyana pakati pemarudzi; vanhu vane machromosome makumi mana nematanhatu (23 pairs), mupunga une makumi maviri nemana, uye mimwe miti inogona kuva nemazana. Kuwedzera kune genome renyukireya, maeukaryotes anewo DNA muorganelles dzakadai semitochondria (munenge mune ese maeukaryotes) uye chloroplasts (mumiti nealgae). DNA iri muorganelles idzi inowanzova diki uye ine majini akakosha ane chekuita nekufema kwemasero kana photosynthesis.
Mukati me genome renyukireya, mune majini anoronga mapuroteni, majini anoronga maRNA (semuenzaniso, rRNA, tRNA, miRNA), uye nzvimbo dzisina kuronga mapuroteni, kazhinji dzakawanda kupfuura nzvimbo dzinoronga mapuroteni. Nzvimbo dzisina kunyora mapuroteni hadzisi hadzo "dzisina basa"; dzakawanda dzadzo dzinoshanda sezvinhu zvinodzora zvakaita sezvinokurudzira, zvinosimudzira, zvinonyaradza, uye zvinodzivirira zvinodzora kana majini ari kushanda.
2. Kurongedza DNA: Kubva kuDouble Helix DNA kusvika kuChromosomes
Kureba kweDNA reeukaryotic kunoshamisa: dai DNA iri musero rimwe chete remunhu ikatambanudzwa, yaizosvika mamita maviri pakureba, kunyangwe nucleus yesero iri dhayamita shoma chete. Dambudziko iri rinokundwa kuburikidza nekurongedza kwakapetwa kakawanda uchishandisa mapuroteni ehistone nemamwe mapuroteni emuviri.
a. Nucleosome: Chikamu Chekutanga cheChromatin
Chikamu chikuru chekurongedza i nucleosome, inova DNA yakaputirwa ne complex yemapuroteni masere e histone (histone octamer). Maviri eDNA angangoita 147 anoputira ma histone, achigadzira chimiro che "beads-on-a-string". Pakati pema nucleosome pane linker DNA strings dzine urefu hwakasiyana, dzinowanzo gadziriswa ne histone H1.
b. Chromatin Fibers uye Advanced Packaging Levels
Nucleosomes hadzimire pachimiro che "beaded"; dzinogona kudyidzana uye kuumba fibers dzakasimba. Kazhinji, idzi dzinowanzonzi fibers dze30-nm, kunyange zvazvo zvinhu izvi zviri mumasero mapenyu zvichichinja-chinja uye hazviwanzofanana. Uyezve, fibers dzechromatin dzinoumba zvishwe zvakasungirirwa ku nucleus protein framework, nokudaro dzichironga DNA munzvimbo.
c. Machromosome eMetaphase
Munguva yekupatsanurwa kwemasero (mitosis nemeiosis), chromatin inoungana zvakasimba kuti igadzire machromosome emetaphase, anoonekwa zviri nyore pasi pemaikorosikopu. Kuungana uku kwakakosha pakupatsanura DNA kuita masero emwanasikana pasina kupwanyika kana kutsemuka.
3. Chromatin: Euchromatin neHeterochromatin
Kurongwa kwemajini kunoenderanawo nekuti DNA "inovhurwa" kana "kuvharwa" sei kuti iwanikwe nemuchina wekunyora zvinyorwa.
– Euchromatin imhando yechromatin yakasununguka, ine majini akawanda anoshanda, uye inonyorwa zviri nyore. Nzvimbo iyi inowanzo "vhurika," zvichiita kuti zvinhu zvinonyora zvinyorwa uye RNA polymerase zvibatane neDNA.
– Heterochromatin imhando yechromatin yakamanikana, kazhinji ine basa shoma rekunyora. Heterochromatin inogona kuva constitutive (inogara yakamanikana, semuenzaniso, pa centromeres ne telomeres) kana kuti facultative (inogona kusiyana zvichienderana nerudzi rwesero kana danho rekukura, semuenzaniso, X chromosome isina kushanda mumhuka dzechikadzi dzinoyamwisa).
Musiyano uyu unoratidza kuti kurongedza DNA hakusi kungori kwemuviri chete, asiwo inzira yekudzora majini.
4. Zvikamu zveChromosomes: Centromeres, Telomeres, uye Mavambo eKudzokorora
Chromosome yega yega ye eukaryotic ine zvikamu zvakakosha zvinovimbisa kugadzikana kwemajini uye nhaka:
– Centromere inzvimbo inoumbwa kinetochores, mapuroteni anobatanidza machromosomes kune spindle fibers panguva yekupatsanurwa kwemasero. Centromere inokosha pakupatsanurwa kwakakodzera kwema chromatids ehanzvadzi.
– MaTelomere ndiwo magumo emachromosome, ane kudzokororwa kwakanangana kweDNA nemapuroteni anodzivirira. MaTelomere anodzivirira magumo emachromosome kuti asaonekwe seDNA yakakuvara uye anodzivirira kusangana pakati pemachromosome. Kupfupika kweTelomere kunoitika panguva yekudzokororwa kweDNA, uye enzyme telomerase inogona kuarebesa mune mamwe masero.
– Kwakatangira kudzokororwa kweDNA (ori) ndipo panotangira kudzokororwa kweDNA. MuEukaryotes, mune maori akawanda pachromosome imwe chete, zvichiita kuti kudzokororwa kuitike nekukurumidza uye zvinobudirira.
5. Magadzirirwo e3D eGenome muNucleus
Ongororo dzemazuva ano dzinoratidza kuti genome harina kurongeka zvisina tsarukano mukati menucleus yesero. DNA iri munzvimbo ine mativi matatu, zvichikanganisa kuratidzwa kwemajini.
a. Nzvimbo yeChromosome
Chromosome yega yega inowanzogara munzvimbo chaiyo munucleus inonzi nzvimbo yechromosome. Kunyangwe paine hukama pakati pemachromosome, kupatsanurwa kwenzvimbo kunobatsira kuchengetedza kurongeka uye kuderedza kusangana.
b. Kutenderedza uye Kubata Nekure
Majini anogona kushandiswa nezvinosimudzira zviri kure asi zviri pedyo nepakati kuburikidza nekuumbwa kwezviropu zvechromatin. Mapuroteni akadai seCTCF necohesin complex anoita basa guru mukuumba nekuchengetedza zviropu izvi.
c. TAD (Madhomini Akabatana Nenzvimbo)
Magene aya akakamurwawo kuita nzvimbo dzekudyidzana dzinonzi maTAD, nzvimbo dzeDNA dzinoshanda pamwe chete kakawanda kupfuura dzimwe nzvimbo. MaTAD anobatsira kuona kuti zvinosimudzira majini "akakodzera" zvinomutsa uye kudzivirira asingadiwe kuti asashande.
6. Epigenetics: Kudzora Majini Pasina Kuchinja Kutevedzana kweDNA
Kurongeka kwema genome eukaryotic kunonyanya kukanganiswa nema epigenetic mechanisms, ayo ari shanduko dzinokanganisa kutaura kwemajini pasina kuchinja DNA base sequence. Maitiro makuru maviri ndeaya:
- Kugadziriswa kweHistone, senge acetylation, methylation, phosphorylation, uye ubiquitination. Histone acetylation inowanzoita kuti chromatin ivhurike zvakanyanya uye inowedzera transcription, nepo mamwe marudzi emethylation anogona kumutsa kana kudzvinyirira transcription zvichienderana nenzvimbo yezvasara.
- DNA methylation, iyo inowanzo kuwanikwa pa cytosines muCpG mumhuka. DNA methylation inowanzobatanidzwa nekudzvinyirirwa kwetranscriptional uye kuumbwa kweheterochromatin.
Epigenetics inobvumira genome imwe chete kugadzira marudzi akasiyana emasero ane mabasa akasiyana, akadai semasero etsinga, masero emhasuru, uye masero eropa, kuburikidza nemapatani akasiyana ekugadzirwa kwemajini.
7. Majini eOrganelle: Mitochondria neChloroplasts
Pamusoro pemajini enyukireya, maeukaryote ane majini emitochondrial, uye mumiti, machloroplast. Majini eOrganellar anowanzo tenderera uye anogara nhaka kubva kuna amai mumarudzi akawanda. Kunyangwe huwandu hwemajini mumitochondria huri hudiki, basa rawo rinokosha pakugadzirwa kwesimba. Zvinofadza kuti majini mazhinji aimbowanikwa mumajini aya akatamira kunucleus panguva yekushanduka-shanduka, saka basa reorganelle rinowanzoenderana nemapuroteni akanyorwa negenome renyukireya.
8. Zvinorehwa neGenome Organization for Health and Evolution
Kurongeka kwemajini kwakakodzera kunoita kuti majini agare zvakanaka. Kukuvara kweTelomere, zvikanganiso pakuumbwa kwechromatin, kana kukanganiswa kwemutemo we epigenetic zvinogona kukonzera zvirwere zvakasiyana-siyana, kusanganisira kenza uye matambudziko ekukura. Semuenzaniso, shanduko mumapatani eDNA methylation dzinogona kumutsa oncogenes kana kudzima majini anodzvinyirira bundu. Uyezve, shanduko mumaumbirwo emachromosome, akadai se translocations, dzinogona kusanganisa majini maviri, zvichikonzera mapuroteni anokuvadza e fusion.
Mukushanduka-shanduka, kurongeka kwemajini kunobvumira kusiyana: kudzokororwa kwemajini, kusanganiswa kwemajini, uye shanduko muzvinhu zvinodzora zvinogona kugadzira mabasa matsva pasina kuchinja sisitimu yese. Saka, kuomarara kwe eukaryotic kunonyanya kukonzerwa nekukwanisa kudzora kunyatsoonekwa kwemajini kuburikidza nesangano remajini rine zvidimbu zvakawanda.
Mhedziso
Kurongeka kwemajini mumasero eukaryotic sisitimu yakarongeka uye ine simba, kubva kumanucleosomes seyuniti yekutanga, kuburikidza nekuumbwa kwe euchromatin ne heterochromatin, kusvika kumagadzirirwo emativi matatu akadai senzvimbo dzema chromosome ne TADs. Mazinga ese aya ekurongeka anoita basa rakakosha mukuona kuti DNA yakabatana, yakachengetedzwa, inodzokororwa, inogarwa nhaka, uye inoburitswa zvichienderana nezvinodiwa nesero. Kuburikidza ne epigenetic mechanisms uye spatial regulation mukati me nucleus, masero eukaryotic anokwanisa kudzora mazana kusvika kuzviuru zvemajini. Kunzwisisa kurongeka kwemajini hakusi kwakakosha chete kune biology yekutanga asiwo kiyi yekunzwisisa zvirwere, kukwegura, uye hunyanzvi hwe biotechnology mune ramangwana.
