Nws yog theem no uas paub qhov txawv ntawm kev siv cov ntaub ntawv caj ces muaj nyob hauv cov hlwb xws li eukaryotes thiab prokaryotes.
Kev txhais lus ntawm lub tswvyim no
Txhais los ntawm Lus Askiv, lo lus no txhais tau tias "ua, ua." Kev ua yog txheej txheem ntawm kev tsim cov mature ribonucleic acid molecules los ntawm pre-RNA. Hauv lwm lo lus, qhov no yog txheej txheej ntawm cov tshuaj tiv thaiv uas ua rau kev hloov pauv ntawm cov khoom lag luam hloov pauv thawj zaug (pre-RNA ntawm ntau hom) rau hauv cov khoom lag luam uas twb muaj lawm.
Raws li kev ua haujlwm ntawm r- thiab tRNA, feem ntau nws nqes los txiav tawm cov seem ntau dhau los ntawm qhov kawg ntawm cov molecules. Yog tias peb tham txog mRNA, ntawm no nws tuaj yeem sau tseg tias hauv eukaryotes cov txheej txheem no tau mus rau ntau theem.
Yog li, tom qab peb tau kawm lawm tias kev ua haujlwm yog kev hloov pauv ntawm cov ntawv sau thawj zaug rau hauv RNA molecule paub tab, nws tsim nyog mus rau kev txiav txim siab nws cov yam ntxwv.
Cov yam ntxwv tseem ceeb ntawm lub tswv yim raws li kev txiav txim siab
Qhov no suav nrog cov hauv qab no:
- hloov kho ntawm ob qhov kawg ntawm cov molecule thiab RNA, thaum lub sijhawm tshwj xeeb nucleotide sequences txuas rau lawv, qhia qhov chaw ntawm qhov pib.(kawg) tshaj tawm;
- splicing - txiav tawm cov ntaub ntawv tsis muaj ntaub ntawv ribonucleic acid uas sib haum rau DNA introns.
Raws li prokaryotes, lawv mRNA tsis raug ua. Nws muaj peev xwm ua haujlwm tam sim ntawd tom qab qhov kawg ntawm kev sib txuas.
txheej txheem nug nyob qhov twg?
Nyob hauv ib yam kab mob, kev ua RNA tshwm sim hauv lub nucleus. Nws yog nqa tawm los ntawm txoj kev tshwj xeeb enzymes (lawv pab pawg) rau txhua tus neeg hom molecule. Cov khoom siv txhais lus xws li polypeptides uas tau nyeem ncaj qha los ntawm mRNA kuj tuaj yeem ua tiav. Lub npe hu ua precursor molecules ntawm feem ntau cov proteins - collagen, immunoglobulins, digestive enzymes, qee cov tshuaj hormones - tau txais cov kev hloov pauv no, tom qab ntawd lawv cov haujlwm tiag tiag hauv lub cev pib.
Peb twb kawm lawm tias kev ua haujlwm yog txheej txheem ntawm kev tsim RNA paub tab los ntawm pre-RNA. Tam sim no nws tsim nyog delving rau hauv qhov xwm ntawm ribonucleic acid nws tus kheej.
RNA: chemical xwm
Nov yog ribonucleic acid, uas yog copolymer ntawm pyrimidine thiab purine ribonucleitides, uas txuas rau ib leeg, ib yam li hauv DNA, los ntawm 3' - 5'-phosphodiester choj.
Txawm hais tias 2 hom molecules no zoo sib xws, lawv txawv ntau txoj hauv kev.
Qhov txawv ntawm RNA thiab DNA
Ua ntej, ribonucleic acid muaj cov pa roj carbon residue, uas pyrimidine thiab purinebases, phosphate pawg - ribose, thaum DNA muaj 2'-deoxyribose.
Thib ob, cov tshuaj pyrimidine kuj txawv. Cov khoom zoo sib xws yog cov nucleotides ntawm adenine, cytosine, guanine. RNA muaj uracil hloov thymine.
Thib peb, RNA muaj 1-stranded qauv, thaum DNA yog 2-stranded molecule. Tab sis cov ribonucleic acid strand muaj thaj tsam ntawm qhov sib txawv polarity (ua raws li kev sib txuas ntxiv) uas tso cai rau nws txoj hlua khi ib leeg kom quav thiab tsim "hairpins" - cov qauv tsim muaj 2-stranded yam ntxwv (raws li qhia hauv daim duab saum toj no)..
Fourthly, vim qhov tseeb tias RNA yog tib txoj hlua uas ua tiav rau tsuas yog ib qho ntawm DNA strands, guanine tsis tas yuav muaj nyob hauv nws hauv tib cov ntsiab lus xws li cytosine, thiab adenine li uracil.
Thib tsib, RNA tuaj yeem hydrolyzed nrog alkali rau 2', 3'-cyclic diesters ntawm mononucleotides. Lub luag haujlwm ntawm cov khoom nruab nrab hauv hydrolysis yog ua los ntawm 2', 3', 5-triester, uas tsis muaj peev xwm tsim nyob rau hauv cov txheej txheem zoo sib xws rau DNA vim tias tsis muaj 2'-hydroxyl pawg hauv nws. Piv rau DNA, alkaline lability ntawm ribonucleic acid yog ib qho khoom muaj txiaj ntsig zoo rau kev kuaj mob thiab tshuaj ntsuam xyuas.
Cov ntaub ntawv muaj nyob rau hauv 1-stranded RNA feem ntau pom tau tias yog ib theem ntawm pyrimidine thiab purine bases, nyob rau hauv lwm yam lus, nyob rau hauv daim ntawv ntawm cov thawj qauv ntawm lub polymer saw.
Qhov no ib ntusntxiv rau cov noob caj noob ces (coding) uas RNA yog "nyeem". Vim tias cov cuab yeej no, ribonucleic acid molecule tuaj yeem khi rau ib coding strand, tab sis tsis muaj peev xwm ua tau nrog cov DNA tsis-coding strand. RNA ib ntus, tshwj tsis yog kev hloov pauv ntawm T nrog U, zoo ib yam li qhov tsis-coding strand ntawm cov noob.
RNA hom
Yuav luag txhua tus ntawm lawv tau koom nrog cov txheej txheem xws li protein biosynthesis. Cov nram qab no hom RNA paub:
- Matrix (mRNA). Cov no yog cytoplasmic ribonucleic acid molecules uas ua raws li cov qauv rau kev tsim cov protein.
- Ribosomal (rRNA). Qhov no yog cytoplasmic RNA molecule uas ua raws li cov khoom siv xws li ribosomes (organelles koom nrog hauv cov protein synthesis).
- Transport (tRNA). Cov no yog cov molecules ntawm thauj ribonucleic acids uas koom nrog hauv kev txhais lus (kev txhais lus) ntawm mRNA cov ntaub ntawv rau hauv cov amino acid ib ntus uas twb muaj nyob hauv cov proteins.
Ib feem tseem ceeb ntawm RNA nyob rau hauv daim ntawv ntawm 1st transcripts, uas yog tsim nyob rau hauv eukaryotic hlwb, nrog rau cov mammalian hlwb, yog raug rau cov txheej txheem ntawm degradation nyob rau hauv lub nucleus, thiab tsis ua si ib tug ntaub ntawv los yog cov yam ntxwv lub luag hauj lwm nyob rau hauv lub cytoplasm.
Hauv tib neeg lub hlwb (cog) ib chav kawm ntawm me me nuclear ribonucleic acids tau pom, uas tsis cuam tshuam ncaj qha rau hauv cov protein synthesis, tab sis cuam tshuam rau kev ua RNA, nrog rau tag nrho cov cellular "architecture". Lawv qhov ntau thiab tsawg sib txawv, lawv muaj 90 - 300 nucleotides.
Ribonucleic acid yog cov khoom tseem ceeb hauv cov noob caj noob cesib tug xov tooj ntawm cov nroj tsuag thiab tsiaj kab mob. Qee tus kab mob RNA yeej tsis mus dhau qhov kev hloov pauv ntawm RNA rau DNA. Tab sis tseem, ntau tus kab mob tsiaj, piv txwv li, retroviruses, yog tus cwj pwm los ntawm kev rov qab txhais lus ntawm lawv RNA genome, qhia los ntawm RNA-dependent reverse transcriptase (DNA polymerase) nrog rau kev tsim ntawm 2-stranded DNA luam. Feem ntau, cov 2-stranded DNA transcript yog nkag mus rau hauv lub genome, ntxiv kev qhia cov kab mob kis thiab tsim cov ntawv luam tshiab ntawm RNA genomes (kuj viral).
Post-transcriptional hloov kho ntawm ribonucleic acid
Nws cov molecules synthesized nrog RNA polymerases ib txwm ua haujlwm tsis ua haujlwm thiab ua raws li cov neeg ua ntej, uas yog pre-RNA. Lawv tau hloov mus rau hauv cov molecules uas twb paub lawm tsuas yog tom qab lawv tau dhau qhov tsim nyog hloov kho tom qab hloov pauv ntawm RNA - theem ntawm nws cov maturation.
Kev tsim ntawm mRNA paub tab pib thaum lub sijhawm sib txuas ntawm RNA thiab polymerase II ntawm theem ntawm elongation. Twb tau mus rau 5'-kawg ntawm maj mam loj hlob RNA strand yog txuas los ntawm 5'-kawg ntawm GTP, ces cov orthophosphate yog cleaved tawm. Tsis tas li ntawd, guanine yog methylated nrog cov tsos ntawm 7-methyl-GTP. Xws li ib pab pawg tshwj xeeb, uas yog ib feem ntawm mRNA, hu ua "cap" (cap lossis cap).
Nyob ntawm hom RNA (ribosomal, thauj, template, thiab lwm yam), precursors undergo ntau yam kev hloov kho raws. Piv txwv li, mRNA precursors undergo splicing, methylation, capping, polyadenylation, thiab qee zaum kho.
Eukaryotes: tag nrhofeature
Lub eukaryotic cell yog lub luag haujlwm ntawm cov kab mob nyob, thiab nws muaj cov nucleus. Ntxiv rau cov kab mob, archaea, txhua yam kab mob yog nuclear. Nroj tsuag, fungi, tsiaj txhu, suav nrog cov kab mob hu ua protists, yog tag nrho cov kab mob eukaryotic. Lawv yog ob leeg 1-celled thiab multicellular, tab sis lawv txhua tus muaj ib qho kev npaj ntawm cellular qauv. Nws feem ntau lees paub tias cov kab mob no, sib txawv, muaj tib lub hauv paus chiv keeb, uas yog vim li cas pawg nuclear tau pom tias yog monophyletic taxon ntawm qib siab tshaj plaws.
Raws li cov kev xav zoo ib yam, eukaryotes originated 1.5 - 2 billion xyoo dhau los. Lub luag haujlwm tseem ceeb hauv lawv cov evolution yog muab rau symbiogenesis - symbiosis ntawm eukaryotic cell uas muaj cov nucleus muaj peev xwm ntawm phagocytosis thiab cov kab mob nqos los ntawm nws - precursors ntawm plastids thiab mitochondria.
Prokaryotes: cov yam ntxwv dav dav
Cov no yog 1-celled cov kab mob uas tsis muaj lub nucleus (tsim), cov seem ntawm daim nyias nyias organelles (sab hauv). Tib lub voj voog loj 2-stranded DNA molecule uas muaj feem ntau ntawm cov cellular cov khoom siv caj ces yog ib qho uas tsis tsim ib qho nyuaj nrog cov proteins histone.
Prokaryotes suav nrog archaea thiab kab mob, suav nrog cyanobacteria. Cov xeeb leej xeeb ntxwv ntawm non-nuclear hlwb - eukaryotic organelles - plastids, mitochondria. Lawv muab faib ua 2 taxa nyob rau hauv lub npe qeb: Archaea thiab Bacteria.
Cov hlwb no tsis muaj lub hnab ntawv nuclear, DNA ntim tshwm sim yam tsis muaj kev koom tes ntawm histones. Hom ntawm lawv cov khoom noj khoom haus yog osmotrophic, thiab cov khoom siv caj cessawv cev los ntawm ib tug DNA molecule, uas yog kaw nyob rau hauv ib lub nplhaib, thiab tsuas muaj 1 replicacon. Prokaryotes muaj cov organelles uas muaj cov qauv membrane.
Qhov txawv ntawm eukaryotes thiab prokaryotes
Qhov tseem ceeb ntawm cov hlwb eukaryotic yog txuam nrog kev muaj cov cuab yeej caj ces hauv lawv, uas nyob hauv lub nucleus, qhov chaw uas nws muaj kev tiv thaiv los ntawm lub plhaub. Lawv DNA yog linear, txuam nrog histone proteins, lwm yam chromosomal proteins uas tsis muaj nyob rau hauv cov kab mob. Raws li txoj cai, 2 theem nuclear muaj nyob rau hauv lawv lub neej voj voog. Ib qho muaj cov chromosomes haploid, thiab tom qab sib koom ua ke, 2 haploid hlwb tsim ib lub cell diploid, uas twb muaj 2 pawg chromosomes. Nws kuj tshwm sim tias thaum lub sij hawm sib faib tom qab, lub cell rov ua haploid. Lub neej zoo li no, nrog rau kev ua haujlwm dav dav, tsis yog tus yam ntxwv ntawm prokaryotes.
Qhov txawv tshaj plaws yog qhov muaj cov organelles tshwj xeeb hauv eukaryotes, uas muaj lawv tus kheej caj ces apparatus thiab rov tsim dua los ntawm kev faib. Cov qauv no yog surrounded los ntawm ib daim nyias nyias. Cov organelles yog plastids thiab mitochondria. Hais txog kev ua haujlwm tseem ceeb thiab cov qauv, lawv kuj xav tsis thoob zoo li cov kab mob. Qhov xwm txheej no ua rau cov kws tshawb fawb xav tias lawv yog cov xeeb leej xeeb ntxwv ntawm cov kab mob uas nkag mus rau hauv kev sib koom ua ke nrog eukaryotes.
Prokaryotes muaj ob peb lub cev, tsis muaj leej twg nyob ib puag ncig los ntawm daim nyias nyias. Lawv tsis muaj endoplasmic reticulum, Golgi apparatus, thiab lysosomes.
Lwm qhov sib txawv tseem ceeb ntawm eukaryotes thiab prokaryotes yog qhov muaj qhov tshwm sim ntawm endocytosis hauv eukaryotes, suav nrog phagocytosis hauvfeem ntau pawg. Cov tom kawg yog lub peev xwm los ntes los ntawm kev kaw hauv cov npuas npuas, thiab tom qab ntawd zom cov khoom sib txawv. Cov txheej txheem no muab kev tiv thaiv tseem ceeb tshaj plaws hauv lub cev. Qhov tshwm sim ntawm phagocytosis yog suav tias yog vim qhov tseeb tias lawv cov hlwb ntawm qhov nruab nrab. Cov kab mob prokaryotic, ntawm qhov tod tes, yog qhov tsis txaus ntseeg me me, uas yog vim li cas thaum lub sijhawm hloov pauv ntawm eukaryotes, kev xav tau tshwm sim cuam tshuam nrog kev muab cov khoom noj ntawm tes nrog cov khoom noj tseem ceeb. Raws li qhov tshwm sim, thawj cov neeg tua tsiaj tau sawv ntawm lawv.
Ua raws li ib qho ntawm cov kauj ruam hauv cov protein biosynthesis
Qhov no yog kauj ruam thib ob uas pib tom qab kev sau ntawv. Kev ua cov protein tshwm sim tsuas yog hauv eukaryotes. Qhov no yog mRNA maturation. Yuav kom meej, qhov no yog tshem tawm cov cheeb tsam uas tsis code rau ib tug protein, thiab ntxiv ntawm kev tswj.
Zoo kawg
Kab lus no piav qhia txog kev ua haujlwm li cas (biology). Nws kuj qhia tias RNA yog dab tsi, teev nws hom thiab kev hloov pauv tom qab hloov pauv. Cov yam ntxwv tshwj xeeb ntawm eukaryotes thiab prokaryotes raug suav hais tias yog.
Thaum kawg, nws tsim nyog nco qab tias kev ua haujlwm yog txheej txheem ntawm kev tsim RNA paub tab los ntawm pre-RNA.
