Te Whakahaere Ira i roto i ngā Pūtau Eukaryotic
He uaua, he tino raupapa hoki te whakaritenga o ngā ira o ngā pūtau eukaryotic—pērā i ngā ira o ngā kararehe, ngā tipu, ngā harore, me ngā protists. Kāore i rite ki ngā prokaryotes, he ira porowhita kei roto i te rohe kotahi (te nucleoid), ka rongoatia e ngā pūtau eukaryotic te nuinga o ā rātou rauemi ira i roto i te karihi i roto i te āhua o ngā chromosomes rārangi. Hei whakauru i te ira roa ki roto i te karihi iti, me te noho ngāwari ki te uru atu mō te whakaaturanga ira me te tāruarua, kua whakawhanakehia e ngā pūtau eukaryotic he pūnaha tākai ira whai hua me te hihiri. Ehara tēnei whakaritenga ira i te mea "rokiroki" noa iho, engari ko te "whakahaere" hoki i te wā me te wāhi e mahi ai ngā ira.
1. Ngā Wāhanga Matua o te Ira Eukaryotic
Ko te ira eukaryotic he mea tito mai i te DNA kua whakarōpūtia ki roto i ētahi ira. He rerekē te maha o ngā ira i waenga i ngā momo; e 46 ngā ira o te tangata (23 ngā takirua), e 24 ngā ira o te raihi, ā, ka taea e ētahi tipu te whai rau. Haunga te ira karihi, kei roto anō hoki i ngā ira eukaryote te ira i roto i ngā whekau pēnei i te mitochondria (i roto i te nuinga o ngā eukaryote) me ngā chloroplast (i roto i ngā tipu me ngā rimurimu). He iti ake te ira i roto i ēnei whekau, ā, kei roto i a rātou ngā ira nui e pā ana ki te manawa pūtau, te whakaahua rānei.
I roto i te ira matua, kei reira ngā ira e whakakōwae ana i te pūmua, ngā ira e whakakōwae ana i te RNA (hei tauira, rRNA, tRNA, miRNA), me ngā rohe kore-kōwae, he maha atu i ngā rohe e whakakōwae ana i ngā pūmua. Ehara i te mea he "koretake" ngā rohe kore-kōwae; he maha o rātou e mahi ana hei wāhanga whakahaere pērā i ngā kaiwhakatairanga, ngā whakarei ake, ngā whakangū, me ngā ārai e whakahaere ana i te wā e kaha ana ngā ira.
2. Te Tākai DNA: Mai i te DNA Helix Takirua ki ngā Chromosome
He mea whakamiharo te roa o te DNA eukaryotic: mēnā ka totorohia te DNA i roto i te pūtau tangata kotahi, ka eke ki te rua mita te roa, ahakoa he torutoru maikiromita noa te whānui o te karihi pūtau. Ka taea te wikitoria i tēnei wero mā te takai maha-paparanga mā te whakamahi i ngā pūmua histone me ētahi atu pūmua hanganga.
a. Nucleosome: Te Wāhanga Taketake o te Chromatin
Ko te taumata taketake o te takai ko te nucleosome, he DNA e takai ana i te matatini o ngā pūmua histone e waru (he histone octamer). Tata ki te 147 ngā takirua turanga o te DNA e takai ana i ngā histone, e hanga ana i tētahi hanganga "piripiri-i-runga-i-te-aho". Kei waenganui i ngā nucleosome he aho DNA hononga o ngā roa rerekē, he maha ngā wā ka whakauhia e te histone H1.
b. Ngā muka Chromatin me ngā taumata takai matatau
Kāore ngā nucleosomes e mutu i te hanganga "piripiri"; ka taea e rātou te taunekeneke me te hanga muka kiato ake. I roto i ngā tikanga tawhito, ka kiia ēnei he muka 30-nm, ahakoa he kaha ake ngā taipitopito o ēnei hanganga i roto i ngā pūtau ora, ā, kāore i te ōrite tonu. Hei tāpiri, ka hangaia e ngā muka chromatin he koropiko e piri ana ki te anga pūmua karihi, ā, ka whakarite i te DNA i te wāhi.
c. Ngā Ira-ira o te Metaphase
I te wā o te wehenga pūtau (mitosis me te meiosis), ka whakapūmau te chromatin hei hanga i ngā chromosomes metaphase, e kitea ngāwari ana i raro i te karuārai. He mea nui tēnei whakapūmautanga mō te wehewehe tika i te DNA ki ngā pūtau tamahine me te kore e raruraru, e whati rānei.
3. Chromatin: Euchromatin me te Heterochromatin
E pā ana hoki te whakaritenga o te ira ki te āhua o te "whakatuwhera" me te "katia" o te DNA kia uru atu ai mā te mīhini whakawhiti ira.
– He momo chromatin ngāwari ake te Euchromatin, he nui ake ngā ira hohe, ā, he ngāwari ake te tuhi. He "tuwhera" ake tēnei rohe, e āhei ai ngā take tuhi me te RNA polymerase ki te here ki te DNA.
– He momo chromatin kiato ake te heterochromatin, he iti te mahi whakawhitiwhiti kōrero i te nuinga o te wā. Ka taea e te heterochromatin te noho pūmau (kiato tonu, hei tauira, i ngā centromere me ngā telomere) te noho ā-pūtau rānei (ka rerekē pea i runga i te momo pūtau, i te wāhanga whanaketanga rānei, hei tauira, te ira-X kua whakakorengia i roto i ngā kararehe uwha).
E whakaatu ana tēnei rerekētanga ehara i te mea ā-tinana anake te takai DNA, engari he tikanga anō hoki mō te whakahaere ira.
4. Ngā Huānga Hanganga o ngā Ira-ira : Te Pūtahi, Teromere, me te Pūtake o te Whakatakotoranga
He wāhanga matua kei ia ira-kōrome eukaryotic hei whakarite i te pumau me te tuku iho ira:
– Ko te centromere te rohe e hangaia ai ngā kinetochores, arā, ngā hanganga pūmua e hono ana i ngā chromosomes ki ngā muka spindle i te wā o te wehenga pūtau. He mea nui te centromere mō te wehenga tika o ngā chromatids tuahine.
– Ko ngā telomere ngā pito o ngā chromosome, he mea hanga mai i ngā tāruarua motuhake o te DNA me ngā pūmua tiaki. Ka ārai ngā telomere i te whakaaro ko ngā pito o te chromosome he DNA kua pakaru, ā, ka ārai hoki i te hanumitanga i waenga i ngā chromosome. Ka puta te whakapoto o ngā telomere i te wā e tāruaruatia ana te DNA, ā, ka taea e te whākōkī telomerase te whakaroa i a rātou i roto i ētahi pūtau.
– Ko te pūtake o te tāruaruatanga (ori) te tīmatanga o te tāruaruatanga DNA. I roto i ngā eukaryote, he maha ngā oris i runga i te ira kotahi, e āhei ai te tere me te whai hua o te tāruaruatanga.
5. Te Hanganga 3D o te Ira i roto i te Pūnaha
E whakaatu ana ngā rangahau hou kāore te ira tangata i whakaritea matapōkeretia i roto i te karihi pūtau. Kei roto te ira tangata i te wāhi toru-ahu, e awe ana i te whakaaturanga ira.
a. Rohe o te Ira-ira
Kei ia ira-kōrome te nuinga o te wā e nohoia ana e ia ira-kōrome tētahi wāhi motuhake i roto i te karihi e kiia nei ko te rohe ira-kōrome. Ahakoa he taunekeneke i waenga i ngā ira-kōrome, ka āwhina te wehenga rohe ki te pupuri i te tikanga me te whakaiti i te raruraru.
b. Te Hurihuri me te Whakapā Mamao
Ka taea te whakahohe i ngā ira mā roto i ngā whakarei ake e tawhiti ana i te taha rārangi engari e tata ana i te taha ā-wāhi mā roto i te hanganga o ngā koropiko chromatin. He mahi nui tā ngā pūmua pēnei i te CTCF me te matatini cohesin ki te hanga me te pupuri i ēnei koropiko.
c. TAD (Ngā Rohe Hononga-Topologically)
Ka wehea hoki te ira tangata ki ngā rohe taunekeneke e kiia nei ko ngā TAD, arā, ngā rohe o te DNA e taunekeneke pinepine ana ki a rātou anō i ētahi atu rohe. Ka āwhina ngā TAD ki te whakarite kia whakahohehia e ngā whakarei ake ngā ira "tika" me te ārai i ngā ira kāore e hiahiatia kia whakahohehia.
6. Epigenetics: Te Whakahaere i ngā Ira me te kore e Huri i te Raupapa DNA
He nui te awe o ngā tikanga epigenetic ki te whakaritenga o ngā ira eukaryotic, arā, ngā huringa e pā ana ki te whakaaturanga ira me te kore e whakarerekē i te raupapatanga turanga DNA . Ko ngā tikanga matua e rua ko:
– Ngā whakarerekētanga histone, pērā i te acetylation, te methylation, te phosphorylation, me te ubiquitination. Ko te tikanga, mā te acetylation histone ka tuwhera ake te chromatin, ka whakanui ake hoki i te tuhi, engari ka taea e ētahi momo methylation te whakahohe, te pehi rānei i te tuhi i runga i te wāhi o te toenga.
– Te methylation DNA, e puta pinepine ana i ngā cytosine i roto i ngā horopaki CpG i roto i ngā kararehe. He maha ngā wā ka honoa te methylation DNA ki te pehitanga o te whakawhitiwhiti kōrero me te hanganga heterochromatin.
Mā te epigenetics ka taea e te ira kotahi te whakaputa i ngā momo pūtau rerekē me ngā mahi rerekē, pērā i ngā pūtau io, ngā pūtau uaua, me ngā pūtau toto, mā roto i ngā tauira rerekē o te whakaaturanga ira .
7. Ngā Ira o te Organelle: Ngā Mitochondria me ngā Chloroplasts
Haunga te ira matua, kei ngā eukaryote ngā ira mitochondrial, ā, i roto i ngā tipu, kei ngā chloroplasts. Ko ngā ira organellar he porowhita te nuinga, ā, he uri tuku iho i roto i te maha o ngā momo. Ahakoa he iti noa te maha o ngā ira i roto i ngā mitochondria, he mea nui tā rātou mahi mō te whakaputa pūngao. He mea whakamīharo, he maha ngā ira i kitea i mua i roto i ēnei organelle kua heke ki te karihi i te wā whanaketanga, nō reira he maha ngā wā ka whakawhirinaki te mahi o ngā organelle ki ngā pūmua i whakakōrerohia e te ira matua.
8. Ngā Pānga o te Whakahaere Ira mō te Hauora me te Whanaketanga
Mā te whakaritenga tika o te ira ka pumau te ira. Mā te kino o te telomere, ngā hapa i roto i te hanganga chromatin, te whakararuraru rānei i te whakahaere epigenetic ka puta ai ngā momo mate, tae atu ki te mate pukupuku me ngā mate whanaketanga. Hei tauira, mā ngā huringa o ngā tauira methylation DNA ka whakahohe i ngā oncogenes, ka whakakore rānei i ngā ira pehi pukupuku. Hei tāpiri, mā ngā huringa o te hanganga chromosome, pērā i te translocations, ka taea te whakakotahi i ngā ira e rua, ka hua ake he pūmua hanumi kino.
I roto i te whanaketanga, ka taea e te whakaritenga o te ira te rerekētanga: ka taea e te tāruarua ira, te whakakotahitanga, me ngā huringa o ngā huānga whakahaere te hanga i ngā mahi hou me te kore e whakarerekē i te pūnaha katoa. Nō reira, ko te uauatanga o te eukaryotic e ahu mai ana i te kaha ki te whakahaere tika i te whakaaturanga ira mā roto i te whakaritenga ira maha-paparanga.
Whakamutunga
He pūnaha tino hanganga, he pūnaha hihiri hoki te whakaritenga ira i roto i ngā pūtau eukaryotic, mai i ngā nucleosome hei waeine taketake, tae atu ki te hanganga o te euchromatin me te heterochromatin, tae atu ki ngā hanganga toru-ahu pērā i ngā rohe chromosome me ngā TAD. He mahi nui tā ēnei taumata whakaritenga katoa ki te whakarite kia whakawhāitihia, kia tiakina, kia tāruatia, kia tukuna iho, kia whakaatuhia hoki te DNA kia rite ki ngā hiahia o te pūtau. Mā roto i ngā tikanga epigenetic me te whakahaere ā-wāhi i roto i te nucleus, ka taea e ngā pūtau eukaryotic te whakahaere tika i ngā rau ki ngā mano o ngā ira. Ko te mārama ki te whakaritenga ira ehara i te mea he mea nui anake mō te koiora taketake engari he mea nui hoki ki te mārama ki te mate, te koroheketanga, me ngā auahatanga hangarau koiora ā muri ake nei.
