Tsarin Halittar Halitta a cikin Kwayoyin Eukaryotic
Kwayoyin halittar ƙwayoyin eukaryotic - kamar na dabbobi, tsirrai, fungi, da protists - suna da tsari mai rikitarwa da tsari mai kyau. Ba kamar prokaryotes ba, waɗanda galibi suna da DNA mai zagaye wanda ke cikin yanki ɗaya (nucleoid), ƙwayoyin eukaryotic suna adana mafi yawan kayan halittarsu a cikin tsakiya a cikin nau'in chromosomes masu layi. Don dacewa da dogon DNA a cikin ƙaramin tsakiya yayin da yake kasancewa cikin sauƙin isa ga bayyanar kwayoyin halitta da kwafi, ƙwayoyin eukaryotic sun haɓaka tsarin marufi na DNA mai inganci da ƙarfi. Wannan tsarin kwayoyin halitta ba wai kawai batun "ajiyewa" bane, har ma da "tsara" lokacin da kuma inda kwayoyin halitta ke aiki.
1. Manyan Abubuwan da ke Cikin Tsarin Halittar Eukaryotic
Tsarin halittar eukaryotic ya ƙunshi DNA da aka haɗa zuwa chromosomes da dama. Adadin chromosomes ya bambanta tsakanin nau'ikan halittu; mutane suna da chromosomes 46 (nau'i-nau'i 23), shinkafa tana da 24, kuma wasu tsire-tsire na iya samun ɗaruruwan. Baya ga tsarin halittar nukiliya, eukaryotes kuma suna da DNA a cikin organelles kamar mitochondria (a kusan dukkan eukaryotes) da chloroplasts (a cikin tsire-tsire da algae). DNA a cikin waɗannan organelles yawanci ƙarami ne kuma yana ɗauke da mahimman kwayoyin halitta da suka shafi numfashin ƙwayoyin halitta ko photosynthesis.
A cikin kwayar halittar nukiliya, akwai kwayoyin halittar da ke tattara sunadaran, kwayoyin halittar da ke tattara RNA (misali, rRNA, tRNA, miRNA), da yankunan da ba su tattara sunadaran ba, galibi suna da yawa fiye da yankunan da ke tattara sunadaran. Yankunan da ba su tattara sunadaran ba lallai ne su zama "marasa amfani" ba; da yawa daga cikinsu suna aiki a matsayin abubuwan da ke tsara abubuwa kamar masu haɓakawa, masu haɓaka abubuwa, masu shiru, da masu hana ruwa gudu waɗanda ke sarrafa lokacin da kwayoyin halitta ke aiki.
2. Haɗa DNA: Daga Double Helix DNA zuwa Chromosomes
Tsawon DNA na eukaryotic abu ne mai ban mamaki: idan aka miƙe DNA a cikin ƙwayar halitta guda ɗaya ta ɗan adam, zai kai tsawon mita biyu, duk da cewa ƙwayar halittar tana da diamita kaɗan na micrometers. Ana shawo kan wannan ƙalubalen ta hanyar marufi mai layuka da yawa ta amfani da sunadaran histone da sauran sunadaran tsari.
a. Nucleosome: Asali Nau'in Chromatin
Mafi mahimmancin matakin marufi shine nucleosome, wanda shine DNA wanda aka naɗe a kusa da hadaddun sunadaran histone guda takwas (histone octamer). Kimanin nau'ikan DNA guda 147 na tushe suna naɗe a kusa da histones, suna samar da tsarin "beads-on-a-string". Tsakanin nucleosomes akwai zaren DNA mai haɗin gwiwa masu tsayi daban-daban, waɗanda galibi histone H1 ke daidaita su.
b. Zaren Chromatin da Matakan Marufi Masu Ci gaba
Nucleosomes ba sa tsayawa a tsarin "beaded"; suna iya hulɗa da samar da zaruruwa masu yawa. A al'ada, ana kiran waɗannan zaruruwa masu girman nm 30, kodayake cikakkun bayanai game da waɗannan tsarin a cikin ƙwayoyin halitta masu rai suna da ƙarfi kuma ba koyaushe suke da daidaito ba. Bugu da ƙari, zaruruwan chromatin suna samar da madaukai waɗanda aka makala su zuwa tsarin furotin na nukiliya, don haka suna tsara DNA a sarari.
c. Kwayoyin Halitta Masu Tasowa
A lokacin rabuwar ƙwayoyin halitta (mitosis da meiosis), chromatin yana taruwa sosai don samar da ƙwayoyin metaphase, waɗanda ake iya gani cikin sauƙi a ƙarƙashin na'urar hangen nesa. Wannan tururi yana da mahimmanci don raba DNA zuwa ƙwayoyin 'ya mace daidai ba tare da ya karye ko ya karye ba.
3. Chromatin: Euchromatin da Heterochromatin
Tsarin kwayoyin halitta yana kuma da alaƙa da yadda ake "buɗe" ko "rufe" DNA don samun damar shiga ta hanyar na'urorin kwafi.
– Euchromatin wani nau'in chromatin ne mai sassauƙa, mai wadata a cikin kwayoyin halitta masu aiki, kuma yana da sauƙin rubutawa. Wannan yanki yana da sauƙin "buɗewa," yana bawa abubuwan rubutu da RNA polymerase damar haɗuwa da DNA.
– Heterochromatin wani nau'in chromatin ne mai ƙaramin ƙarfi, gabaɗaya tare da ƙarancin aikin rubutu. Heterochromatin na iya zama mai tsari (koyaushe yana da ƙaramin ƙarfi, misali, a centromeres da telomeres) ko kuma mai tsari (yana iya bambanta dangane da nau'in tantanin halitta ko matakin ci gaba, misali, ƙwayar X da ba ta aiki a cikin dabbobi masu shayarwa na mata).
Wannan bambancin yana nuna cewa marufin DNA ba wai kawai na zahiri bane, har ma da wata hanya ce ta daidaita kwayoyin halitta.
4. Abubuwan Tsarin Kwayoyin Halittar Kwai : Centromere, Telomere, da Asalin Kwafi
Kowace kwayar halittar eukaryotic tana da muhimman sassa waɗanda ke tabbatar da daidaiton kwayoyin halitta da gado:
– Centromere shine yankin da kinetochores ke samar da su, tsarin furotin da ke haɗa chromosomes zuwa zare na spindle yayin rabuwar ƙwayoyin halitta. Centromere yana da mahimmanci don raba chromatids na 'yan'uwa mata yadda ya kamata.
– Telomeres su ne ƙarshen ƙwayoyin halitta, waɗanda suka ƙunshi takamaiman maimaitawar DNA da sunadaran kariya. Telomeres yana hana a ɗauke ƙarshen ƙwayoyin halitta a matsayin DNA da ta lalace kuma yana hana haɗuwa tsakanin ƙwayoyin halitta. Ragewar ƙwayoyin halitta yana faruwa yayin kwafi na DNA, kuma telomerase na enzyme na iya tsawaita su a wasu ƙwayoyin halitta.
– Asalin kwafi (ori) shine wurin fara kwafi na DNA. A cikin eukaryotes, akwai iris da yawa akan chromosome guda ɗaya, wanda ke ba da damar kwafi ya faru cikin sauri da inganci.
5. Tsarin 3D na Tsarin Halittar Halitta a cikin Nucleus
Binciken zamani ya nuna cewa ba a tsara kwayar halittar bazuwar a cikin kwayar halittar ba. DNA yana cikin sararin samaniya mai girma uku, yana tasiri ga bayyanar kwayar halitta.
a. Yankin Kwayoyin Halitta
Kowace kwayar halitta tana mamaye wani yanki na musamman a cikin kwayar halitta da ake kira yankin chromosome. Duk da cewa akwai hulɗa tsakanin kwayoyin halitta, rabuwar yankuna yana taimakawa wajen kiyaye tsari da rage tangarda.
b. Zagaye da Lambobin Sadarwa Daga Nesa
Kwayoyin halitta za su iya kunnawa ta hanyar masu haɓaka waɗanda ke nesa da juna amma suna kusa da juna ta hanyar ƙirƙirar madaukai na chromatin. Sunadaran kamar CTCF da haɗin cohesin suna taka muhimmiyar rawa wajen ƙirƙirar da kuma kula da waɗannan madaukai.
c. TAD (Yankunan da ke da alaƙa da yanayin ƙasa)
An kuma raba kwayar halittar zuwa sassan hulɗa da ake kira TADs, yankuna na DNA waɗanda ke hulɗa akai-akai da kansu fiye da sauran yankuna. TADs suna taimakawa wajen tabbatar da cewa masu haɓakawa suna kunna kwayoyin halittar "dama" kuma suna hana waɗanda ba a so su kunna.
6. Epigenetics: Daidaita Kwayoyin Halitta Ba Tare da Canza Jerin DNA ba
Tsarin kwayoyin halittar eukaryotic yana da matuƙar tasiri ta hanyar hanyoyin epigenetic, waɗanda canje-canje ne da ke shafar bayyanar kwayoyin halitta ba tare da canza jerin tushen DNA ba . Manyan hanyoyin guda biyu sune:
– Gyaran Histone, kamar acetylation, methylation, phosphorylation, da ubiquitination. Histone acetylation gabaɗaya yana sa chromatin ya fi buɗewa kuma yana ƙara rubutun, yayin da wasu nau'ikan methylation na iya kunnawa ko danne rubutun dangane da wurin da ragowar yake.
– Tsarin halittar DNA, wanda yawanci ke faruwa a cytosines a cikin mahallin CpG a cikin dabbobi. Tsarin halittar DNA sau da yawa yana da alaƙa da danne rubutun bayanai da samuwar heterochromatin.
Epigenetics yana bawa kwayar halitta iri ɗaya damar samar da nau'ikan ƙwayoyin halitta daban-daban tare da ayyuka daban-daban, kamar ƙwayoyin jijiya, ƙwayoyin tsoka, da ƙwayoyin jini, ta hanyar nau'ikan bayyanar kwayoyin halitta daban-daban .
7. Kwayoyin Halittar Organelle: Mitochondria da Chloroplasts
Baya ga kwayar halittar nukiliya, eukaryotes suna da kwayoyin halittar mitochondrial, kuma a cikin tsire-tsire, chloroplasts. Kwayoyin halittar gabobi gabaɗaya suna da zagaye kuma ana gadon su ta hanyar uwa a cikin nau'ikan halittu da yawa. Duk da cewa adadin kwayoyin halittar da ke cikin mitochondria ƙarami ne, aikinsu yana da mahimmanci don samar da makamashi. Abin sha'awa, kwayoyin halittar da aka samo a baya a cikin waɗannan kwayoyin halittar sun ƙaura zuwa tsakiya yayin juyin halitta, don haka aikin organelle sau da yawa ya dogara ne akan sunadaran da kwayar halittar nukiliya ta ƙunsa.
8. Tasirin Tsarin Halittar Jini don Lafiya da Juyin Halitta
Tsarin kwayoyin halitta mai kyau yana tabbatar da kwanciyar hankali na kwayoyin halitta. Lalacewar telomere, kurakurai a cikin samuwar chromatin, ko rushewar tsarin epigenetic na iya haifar da cututtuka daban-daban, gami da ciwon daji da matsalolin ci gaba. Misali, canje-canje a cikin tsarin methylation na DNA na iya kunna oncogenes ko kashe kwayoyin halittar da ke rage ciwace-ciwacen daji. Bugu da ƙari, canje-canje a cikin tsarin chromosome, kamar translocations, na iya haɗa kwayoyin halitta guda biyu, wanda ke haifar da sunadaran haɗuwa masu cutarwa.
A cikin juyin halitta, tsarin kwayoyin halitta yana ba da damar bambance-bambance: kwafi na kwayoyin halitta, sake haɗawa, da canje-canje a cikin abubuwan da ke daidaita tsarin na iya ƙirƙirar sabbin ayyuka ba tare da canza tsarin gaba ɗaya ba. Don haka, sarkakiyar eukaryotic galibi tana tasowa ne daga ikon daidaita bayyanar kwayoyin halitta ta hanyar tsarin kwayoyin halitta mai matakai da yawa.
Kammalawa
Tsarin kwayoyin halitta a cikin ƙwayoyin eukaryotic tsari ne mai tsari da ƙarfi, tun daga nucleosomes a matsayin naúrar asali, ta hanyar ƙirƙirar euchromatin da heterochromatin, zuwa gine-gine masu girma uku kamar yankunan chromosomes da TADs. Duk waɗannan matakan tsari suna taka muhimmiyar rawa wajen tabbatar da cewa an taurare DNA, an kare shi, an kwafi shi, an gada shi, kuma an bayyana shi bisa ga buƙatun tantanin halitta. Ta hanyar hanyoyin epigenetic da kuma daidaita sararin samaniya a cikin tsakiya, ƙwayoyin eukaryotic suna iya sarrafa daidai ɗaruruwan zuwa dubban kwayoyin halitta. Fahimtar tsarin kwayoyin halitta ba wai kawai yana da mahimmanci ga ilimin halittar asali ba har ma yana da mahimmanci don fahimtar cututtuka, tsufa, da sabbin abubuwan da suka faru na fasahar halittu na gaba.
