Zitsanzo za Mafunso Okhudza Kukonzekera kapena Kuyika kwa DNA mu Maselo
Pegantar
DNA, kapena deoxyribonucleic acid, ndi molekyulu yomwe imanyamula chidziwitso cha majini m'zamoyo. Mkati mwa maselo, DNA iyenera kuyikidwa bwino kwambiri kuti igwirizane ndi nucleus yaying'ono pomwe ikukhalabe yotheka kuchita zinthu zofunika kwambiri monga kubwerezabwereza ndi kulemba. Kukonza ndi kuyika DNA kumeneku kumaphatikizapo zigawo ndi kapangidwe kake ka zinthu zambiri, kuphatikizapo mapuloteni a histone ndi chromatin. M'nkhaniyi, tikambirana zitsanzo za mavuto okhudzana ndi kukonza DNA ndi mayankho ake.
Funso 1: Fotokozani momwe DNA imafupikitsidwira mu nucleus ya maselo a eukaryotic.
Yankho:
Kuyika DNA movutikira kumayamba ndi kupanga mapangidwe otchedwa nucleosomes. Nucleosomes ndi mayunitsi oyambira a chromatin, omwe amakhala ndi gawo la DNA pafupifupi ma base pairs 147 omwe amazunguliridwa mozungulira mapuloteni asanu ndi atatu a histone. Ma histones ndi mapuloteni ang'onoang'ono, okhala ndi positive charge omwe amalola DNA yomwe ili ndi negative charge kuti izizungulira mozungulira.
Nucleosome iliyonse imalumikizidwa ndi gawo lalifupi la linker DNA, lofanana ndi "mikanda pa chingwe." Pamene ma phukusi awa aphatikizidwa, kapangidwe kake kamaphatikizidwanso kukhala ulusi wokhuthala wa chromatin, pafupifupi 30 nm m'lifupi, wotchedwa solenoid kapena zigzag.
Kenako ma solenoid amapindidwanso pogwiritsa ntchito mapuloteni a scaffold kukhala okhuthala, zomwe zimapangitsa kuti ma chromosome azioneka panthawi yogawa maselo. Panthawi ya interphase, chromatin ikhoza kukhalapo mu heterochromatin (yokhala ndi ma complex ambiri ndipo nthawi zambiri imakhala yosagwira ntchito) ndi euchromatin (yokhala ndi ma complex ochepa komanso yogwira ntchito pang'ono).
Funso 2: Kodi zowongolera kapena zosintha za histone zimagwira ntchito bwanji powongolera momwe majini amagwirira ntchito?
Yankho:
Ma Histones amasinthidwa m'njira zosiyanasiyana, monga methylation, acetylation, phosphorylation, ndi ubiquitination, zomwe zimathandiza kwambiri pakulamulira momwe majini amagwirira ntchito. Kusintha kumeneku kungakhudze momwe chromatin imakhalira yomasuka kapena yofupikitsidwa, motero kumakhudza kupezeka kwa DNA ku makina olembera:
1. Kuchuluka kwa Histone Acetylation: Kuwonjezera magulu a acetyl ku zotsalira za histone lysine ndi ma enzyme a histone acetyltransferase (HAT) kumachepetsa mphamvu yabwino ya ma histone, motero kumachepetsa kuyanjana kwawo ndi DNA ndikupangitsa chromatin yofooka. Kuchuluka kwa chromatin kumathandiza kupeza mosavuta zinthu zolembera, motero kumawonjezera kufotokozera kwa majini.
2. Histone Methylation: Kuwonjezera magulu a methyl kungayambitse kapena kuletsa kufalikira kwa majini kutengera malo ndi momwe zinthu zilili. Mwachitsanzo, methylation ya H3K4 nthawi zambiri imagwirizanitsidwa ndi kuyambitsa majini, pomwe methylation ya H3K9 ndi H3K27 imagwirizanitsidwa ndi kuponderezedwa kwa majini.
3. Phosphorylation ndi Zosintha Zina: Zosintha zina za histone zimathandizanso pa kapangidwe ndi ntchito ya chromatin, nthawi zambiri pankhani ya mayankho a ma cell signaling ndi kuzungulira kwa ma cell.
Ponseponse, kusintha kwa histone kumapereka "khodi ya histone" yomwe imawonetsa momwe majini ena amaonekera mu selo ndipo imayankha kusintha kwa chilengedwe kapena momwe maselo amakhalira.
Funso 3: Mu kafukufuku, chidutswa cha DNA chinapezeka kuti chili ndi kutalika kwa 10.000 bp. Pambuyo pochipatula ndi kuchisanthula, chidutswacho chinapezeka kuti chili ndi ma nucleosome 50. Kutengera ndi izi, kodi kutalika kwa DNA yolumikizira pakati pa ma nucleosome mu chidutswachi ndi kotani?
Yankho:
Kuti tithetse vutoli, tiyenera kudziwa kuti nucleosome iliyonse imazungulira 147 bp ya DNA. Chifukwa chake, ngati pali nucleosome 50, kutalika konse kwa DNA komwe kumazungulira nucleosome ndi:
\[ 147 \text{ bp/nucleosome} \times 50 \text{ nucleosomes} = 7350 \text{ bp} \]
Utali wonse wa DNA ndi 10.000 bp, kotero DNA yonse yolumikizira ndi:
\[ 10.000 \text{ bp} – 7350 \text{ bp} = 2650 \text{ bp} \]
Popeza pali ma linker 49 (linker DNA pakati pa ma nucleosome awiri), kutalika kwapakati pa linker DNA imodzi ndi:
\[ \frac{2650 \text{ bp}}{49} \pafupifupi 54.08 \text{ bp} \]
Motero, kutalika kwapakati pa DNA yolumikizira pakati pa nucleosome iliyonse ndi pafupifupi 54 bp.
Mapeto
Kuyika DNA mkati mwa maselo ndi njira yovuta komanso yolamulidwa bwino, zomwe zimathandiza kusungira bwino chidziwitso cha majini ndikupeza makina ofunikira a mamolekyu. Kudziwa bwino kapangidwe ka DNA, kuphatikizapo kapangidwe ka nucleosome ndi kusintha kwa histone, ndikofunikira kwambiri kuti timvetsetse bwino momwe majini amagwirira ntchito komanso momwe maselo amagwirira ntchito. Zitsanzo zomwe takambirana pamwambapa zimatithandiza kumvetsetsa bwino momwe DNA imasungidwira ndi kukonzedwa mkati mwa nyukiliyasi, pamene tikukulitsa kumvetsetsa kwathu za sayansi ya mamolekyu.
