Hoʻopili hou ʻana o ka DNA ma ka mahele ʻana o ke kelepona
ʻO ka hana hou ʻana o ka DNA ke kaʻina hana o ka hana pālua ʻana i nā mea genetic i loko o kahi cell ma mua o ka māhele ʻana. He mea nui kēia kaʻina hana no ke ola ʻana o kahi meaola, no ka mea, e hōʻoiaʻiʻo ana e loaʻa i kēlā me kēia cell kaikamahine ke kope like o ka ʻike genetic e like me ke cell makua. Me ka ʻole o ka hana hou ʻana o ka DNA pololei, ʻo ka mahele ʻana o ke cell—inā no ka ulu ʻana, ka hoʻoponopono ʻana i nā ʻiʻo, a i ʻole ka hana hou ʻana—e hopena i nā cell me ka ʻike genetic piha ʻole a hōʻino ʻia paha. No laila, ua manaʻo ʻia ka hana hou ʻana o ka DNA ʻo ia kekahi o nā kaʻina hana olaola koʻikoʻi a i kāohi ʻia i loko o ke ola o ke cell.
Ke Kūlana o ka Hoʻopili ʻana o ka DNA i loko o ke Kaʻapuni Kelepona
Hana ʻia ka mahele ʻana o ke kelepona i loko o nā meaola eukaryotic ma o ke kaʻina hana o ke kelepona, ʻo ia hoʻi ka interphase a me ka mahele ʻana (mitosis a i ʻole meiosis). Ua māhele ʻia ʻo Interphase iā G1 (ulu ʻana), S (synthesis DNA), a me G2 (hoʻomākaukau no ka mahele ʻana). Hana ʻia ka hana hou ʻana o ka DNA i ka pae S, i ka wā e kope ai ke kelepona i kāna mau chromosome āpau. Ma hope o ka pau ʻana o kēia pae, ʻaʻole kēlā me kēia chromosome he mole DNA hoʻokahi akā aia i ʻelua mau chromatids kaikuahine like i hoʻopili ʻia ma ka centromere. ʻO kēia kūlana "ʻelua kope" e ʻae i ka hoʻolaha like ʻana o nā mea genetic i ka wā mitosis a i ʻole meiosis.
I ka mitosis, ʻo ka hopena hope loa he ʻelua mau cell kaikamahine like like. I ka meiosis, ʻo ka pahuhopu ka hana ʻana i nā cell sex (gametes) me ka hapalua o ka helu o nā chromosomes. No laila, hana ʻia ka hana hou ʻana o ka DNA i hoʻokahi manawa ma mua o ka meiosis I, a ukali ʻia e ʻelua mau mahele hope. He mea koʻikoʻi ka pololei o ka hana hou ʻana o ka DNA i nā hihia ʻelua, no ka mea, hiki i nā hewa ke alakaʻi i nā mutations, nā ʻano chromosomal, a i ʻole ka hāʻule ʻana o ka ulu ʻana.
ʻO ke ʻano o ka DNA a me nā kumumanaʻo kumu o ka hana hou ʻana
Ua haku ʻia ka DNA me ʻelua mau kaula (he helix pālua) e hui pū ana ma o nā pilina hydrogen ma waena o nā kumu nitrogenous: ʻo adenine (A) e hui pū me thymine (T), ʻoiai ʻo guanine (G) e hui pū me cytosine (C). Mālama kēia kaʻina kumu i ka ʻike genetic. I ka wā o ka hana hou ʻana, hoʻokaʻawale ʻia nā kaula DNA ʻelua, e lawelawe ana kēlā me kēia ma ke ʻano he template no ka hoʻokumu ʻana i kahi kaula hou, hoʻopihapiha. Ua ʻike ʻia kēia kumumanaʻo ʻo ka hoʻohui kumu hoʻopihapiha.
He semiconservative ka hana hou ʻana o ka DNA, ʻo ia hoʻi, aia kēlā me kēia molekole DNA i hana hou ʻia i hoʻokahi kaula kahiko (makua) a me hoʻokahi kaula hou. Ua hōʻike ʻia ke kumumanaʻo o ka semiconservativeness ma o ka hoʻokolohua maʻamau a Meselson lāua ʻo Stahl i ka makahiki 1958, kahi i hōʻike ai e hoʻohana nā cell i ke kaula kahiko ma ke ʻano he alakaʻi i hiki ai i nā hopena ke kūpaʻa i ka moʻo DNA mua.
Nā Pae Nui o ka Hoʻopili ʻana o ka DNA
Ma keʻano laulā, hiki ke hoʻokaʻawale ʻia ka hana hou ʻana o ka DNA i ʻekolu mau pae: ka hoʻomaka ʻana, ka hoʻolōʻihi ʻana, a me ka hoʻopau ʻana. ʻOiai ke ʻano maʻalahi, pili kēlā me kēia pae i nā ʻano enzyme like ʻole a me nā protein kākoʻo.
1. Hoʻomaka: Hoʻomaka o ka hana hou ʻana ma ke kiko kumu
Hoʻomaka ka hana hou ʻana ma kahi kikoʻī i loko o ka DNA i kapa ʻia ʻo ke kumu o ka hana hou ʻana (ori). I loko o nā meaola prokaryotic, hoʻokahi wale nō ori ma kahi chromosome poepoe. I loko o nā eukaryotes, ma muli o ko lākou genomes nui aʻe, aia nā oris he nui ma kēlā me kēia chromosome e ʻae ai i ka hana hou wikiwiki.
I kēia pae, wehe ka enzyme helicase i ka helix pālua ma ka uhaki ʻana i nā pilina hydrogen ma waena o nā kumu, e hana ana i kahi ʻano i kapa ʻia he fork replication. ʻO ka hoʻokaʻawale ʻana o nā kaula DNA e hana i ke kaumaha torsional i loko o ka DNA i wehe ʻia, no laila kōkua ka enzyme topoisomerase i ka hoʻomaha ʻana i kēia haunaele e pale aku i ka DNA mai ka hihia a haki paha.
I mea e pale ai i ka hui hou ʻana o nā kaula DNA i hoʻokaʻawale ʻia, hoʻopili nā protein hoʻopaʻa kaula hoʻokahi (SSB) i nā kaula hoʻokahi a mālama iā lākou i ka paʻa ma ke kaʻina hana.
2. Elongation: Hoʻokumu ʻia ʻana o nā kaula DNA hou
ʻO ke kahua elongation ke kaʻina hana o ka hoʻohui ʻana i nā nucleotides e hana i kahi kaula DNA hou. ʻO ka enzyme nui e hana nei ma ʻaneʻi ʻo ia ka DNA polymerase. Eia naʻe, ʻaʻole hiki i ka DNA polymerase ke hoʻomaka i ka synthesis mai ka wā kahiko; pono ia i kahi "wahi hoʻomaka" ma ke ʻano o kahi primer. Hana ʻia kēia primer e ka enzyme primase, kahi ʻāpana pōkole o RNA e hāʻawi ana i kahi hopena 3'-OH ma ke ʻano he wahi hoʻomaka no ka hoʻohui ʻana i ka nucleotide.
Hoʻohui wale ka DNA polymerase i nā nucleotides ma ke kuhikuhi 5' a 3'. No ka mea, holo nā kaula ʻelua o ka DNA i nā ʻaoʻao ʻē aʻe (antiparallel), ʻokoʻa ke ʻano o ka hana hou ʻana ma kēlā me kēia kaula:
– Hoʻohui mau ʻia ke kaula alakaʻi ma ke kuhikuhi o ka neʻe ʻana o ka ʻōpuʻu replication.
– Hoʻohui ʻia ke kaula lagging me ka hoʻomau ʻole mai ka ʻōpuʻu replication, e hana ana i nā ʻāpana pōkole i kapa ʻia ʻo nā ʻāpana Okazaki.
Ke hoʻokumu ʻia nā ʻāpana Okazaki, pono e wehe ʻia ka primer RNA a hoʻololi ʻia me ka DNA. I loko o nā prokaryotes, wehe ka DNA polymerase I i ka primer a hoʻololi iā ia. I loko o nā eukaryotes, pili kēia kaʻina hana iā RNase H a me kahi DNA polymerase kikoʻī. A laila hoʻohui ka DNA ligase i nā ʻāpana e hana i kahi kaula lagging piha.
3. Hoʻopau: Hoʻopau i ka hana hou ʻana
Hana ʻia ka hoʻopau ʻana i ka wā e hui ai nā ʻōpuʻu hoʻohālikelike a i ʻole i ka wā i pāpālua ʻia ai nā DNA āpau. I loko o nā prokaryotes, kōkua kahi kaʻina hoʻopau kūikawā i ka hoʻōki ʻana i ka hoʻohālikelike. I loko o nā eukaryotes, ʻoi aku ka paʻakikī o ke kaʻina hana no ka mea neʻe nā ʻōpuʻu hoʻohālikelike he nui a me nā kumu i nā ʻaoʻao like ʻole a hiki i ka wā e hui hope ai lākou.
ʻO kekahi o nā pilikia nui i nā eukaryotes ka hana hou ʻana o nā wēlau o nā chromosomes linear, i ʻike ʻia ʻo telomeres. Ma muli o ke ʻano o ka DNA polymerase, ʻaʻole hiki ke hana hou ʻia nā wēlau DNA ma ke kaula lagging, no laila e pōkole nā chromosomes i kēlā me kēia manawa e māhele ai kahi cell. Kōkua ka enzyme telomerase i ka lanakila ʻana i kēia pilikia ma ka hoʻohui ʻana i nā kaʻina hana hou i nā telomeres, ʻoi aku hoʻi i kekahi mau cell e like me nā cell germ a me kekahi mau cell stem. Pili ka hana telomerase i kāohi ʻole ʻia me ka hiki ke māhele mau loa i nā cell cancer he nui.
Ka Pololei o ke Kope ʻana a me nā ʻAno Hoʻoponopono
Pono ka hana hou ʻana o ka DNA e pololei loa no ka mea hiki i nā hewa liʻiliʻi ke loaʻa nā hopena koʻikoʻi i ka hana protein a me ka hoʻoponopono ʻana o ka gene. Loaʻa i ka DNA polymerase nā hiki ke hoʻoponopono, kahi e nānā pālua ai i nā nucleotides i hoʻokomo hou ʻia. Inā loaʻa kahi hui kumu hewa, hiki i ka DNA polymerase ke wehe iā ia ma o ka hana exonuclease a hoʻololi iā ia me ka mea kūpono.
Ma waho aʻe o ka hoʻoponopono ʻana, loaʻa pū i nā cell nā ʻōnaehana hoʻoponopono DNA ma hope o ke kope ʻana, e like me ka hoʻoponopono mismatch, kahi e ʻike ai i nā hewa hui kumu e pakele ana i ka hoʻoponopono ʻana. ʻO kēia hui pū ʻana o nā ʻano hana e hopena i kahi helu hewa kope haʻahaʻa loa, ʻoiai hiki ke hoʻoili ʻia nā mutations i nā cell kaikamahine.
ʻO ke kope DNA ma ke ʻano he kī i ka mahele cell holomua
Ua pili pono ka hana hou ʻana o ka DNA a me ka mahele ʻana o ke kelepona. Inā ʻaʻole piha a hōʻino ʻia paha ka hana hou ʻana, hoʻōki pinepine nā kelepona i ke kaʻina hana o ke kelepona ma o nā wahi nānā e pale aku i ka mahele ʻana me ka DNA i hōʻino ʻia. Hana kēia mau wahi nānā e like me kahi ʻōnaehana hoʻomalu maikaʻi: ʻae ʻia nā kelepona e komo i ka mitosis inā ua kope piha ʻia kā lākou DNA a ʻaʻohe pohō nui.
Inā hāʻule nā wahi nānā a i ʻole e hala ʻia, hiki i nā pūnaewele ke māhele me ka DNA paʻa ʻole, e alakaʻi ana i nā chromosomal imbalances, ka hōʻiliʻili ʻana i nā mutations, a me ka hoʻonui ʻana i ka pilikia o ka maʻi kanesa. No laila, ʻo ka hoʻomaopopo ʻana i ka hana hou ʻana o ka DNA ʻaʻole wale ia he mea nui no ka biology kumu akā he mea pili pū kekahi i ka lāʻau lapaʻau, ʻoi aku hoʻi i ka noiʻi maʻi genetic a me ka hoʻomohala ʻana i nā lāʻau lapaʻau kanesa.
Ka hopena
ʻO ka hana hou ʻana o ka DNA i ka wā o ka mahele ʻana o ke kelepona he hana olaola koʻikoʻi ia e hōʻoiaʻiʻo ana i ka hoʻoili pololei ʻana o ka ʻike genetic mai kekahi hanauna o nā kelepona a i kekahi. Hana ʻia kēia kaʻina hana i ka wā S o ke kaʻina hana kelepona a pili i ka laulima ʻana o nā enzymes like ʻole e like me helicase, primase, DNA polymerase, ligase, a me nā protein kākoʻo ʻē aʻe. Ma o nā ʻano hana semiconservative, ka synthesis kaula alakaʻi a me ka lagging, a me nā ʻōnaehana hoʻoponopono a me ka hoʻoponopono DNA, hiki i nā kelepona ke hana hou i kā lākou genomes me ka hilinaʻi kiʻekiʻe. ʻO ka hilinaʻi o ka hana hou ʻana o ka DNA e hoʻoholo ai i ka maikaʻi o ka mahele ʻana o ke kelepona a me ke kūpaʻa genetic o kahi meaola, no laila hiki i ka hoʻopilikia ʻana i kēia kaʻina hana ke alakaʻi i nā maʻi genetic a me ke kanesa. ʻO ka hoʻomaopopo ʻana i ka hana hou ʻana o ka DNA ʻo ia hoʻi ka hoʻomaopopo ʻana i kekahi o nā kumumanaʻo koʻikoʻi o ke ola ponoʻī: pehea e mālama ai nā kelepona a hoʻouna i ko lākou ʻano genetic.
