Nucleic acids, tshwj xeeb tshaj yog DNA, paub zoo heev hauv kev tshawb fawb. Qhov no tau piav qhia los ntawm qhov tseeb tias lawv yog cov khoom ntawm lub xov tooj ntawm tes, uas qhov kev khaws cia thiab kev xa tawm ntawm nws cov ntaub ntawv keeb kwm nyob ntawm. DNA, nrhiav tau rov qab rau xyoo 1868 los ntawm F. Miescher, yog ib qho molecule uas muaj cov khoom muaj kua qaub. Tus kws tshawb fawb cais nws los ntawm cov nuclei ntawm leukocytes - cov hlwb ntawm lub cev tiv thaiv kab mob. Tshaj li 50 xyoo tom ntej no, kev tshawb fawb ntawm nucleic acids tau ua tsis tu ncua, txij li feem ntau biochemists suav hais tias cov proteins yog cov organic tseem ceeb, thiab lwm yam, rau cov yam ntxwv ntawm caj ces.
Txij li thaum lub deciphering ntawm DNA qauv ntawm Watson thiab Crick nyob rau hauv 1953, kev tshawb fawb loj pib, uas pom tau tias deoxyribonucleic acid yog ib tug polymer, thiab nucleotides ua raws li DNA monomers. Lawv hom thiab qauv yuav raug kawm los ntawm peb hauv txoj haujlwm no.
Nucleotides raws li cov qauv ntawm cov ntaub ntawv keeb kwm
Ib qho ntawm cov khoom tseem ceeb ntawm cov khoom muaj sia yog kev khaws cia thiab xa cov ntaub ntawv hais txog cov qauv thiab kev ua haujlwm ntawm ob lub cell thiab tag nrho cov kabmob.feem ntau. Lub luag haujlwm no yog ua los ntawm deoxyribonucleic acid, thiab DNA monomers - nucleotides yog ib hom "cib" los ntawm cov qauv tsim tshwj xeeb ntawm cov khoom tsim los ntawm noob neej. Cia peb xav txog dab tsi cov cim tsiaj qus tau coj los ntawm thaum tsim cov nucleic acid supercoil.
Yuav ua li cas nucleotides tsim
Tau teb lo lus nug no, peb xav tau qee qhov kev paub txog organic chemistry. Hauv particular, peb nco qab tias nyob rau hauv qhov xwm txheej muaj ib pawg ntawm nitrogen-muaj heterocyclic glycosides ua ke nrog monosaccharides - pentoses (deoxyribose los yog ribose). Lawv hu ua nucleosides. Piv txwv li, adenosine thiab lwm yam nucleosides muaj nyob rau hauv cytosol ntawm ib lub xovtooj ntawm tes. Lawv nkag mus rau hauv cov tshuaj tiv thaiv esterification nrog orthophosphoric acid molecules. Cov khoom ntawm cov txheej txheem no yuav yog nucleotides. Txhua DNA monomer, thiab muaj plaub hom, muaj lub npe, xws li guanine, thymine, thiab cytosine nucleotides.
YPurine monomers ntawm DNA
Hauv biochemistry, ib qho kev faib tawm yog saws uas faib DNA monomers thiab lawv cov qauv ua ob pawg: piv txwv li, adenine thiab guanine nucleotides yog purine. Lawv muaj derivatives ntawm purine, ib qho organic tshuaj nrog cov mis C5H4N44. DNA monomer, guanine nucleotide, kuj muaj purine nitrogenous puag txuas nrog deoxyribose los ntawm N-glycosidic daim ntawv cog lus hauv beta configuration.
YPyrimidine nucleotides
Nitrogenous puag,hu ua cytidine thiab thymidine, yog derivatives ntawm cov organic pyrimidine. Nws cov qauv yog C4H4N2. Lub molecule yog ib tug rau-membered planar heterocycle uas muaj ob nitrogen atoms. Nws paub tias tsis yog thymine nucleotide, ribonucleic acid molecules, xws li rRNA, tRNA, thiab mRNA, muaj uracil monomer. Thaum lub sij hawm transcription, thaum hloov cov ntaub ntawv los ntawm DNA noob mus rau mRNA molecule, lub thymine nucleotide yog hloov los ntawm adenine, thiab adenine nucleotide yog hloov los ntawm uracil nyob rau hauv lub synthesized mRNA saw. Ntawd yog, cov ntaub ntawv hauv qab no yuav ncaj ncees: A - U, T - A.
Chargaff rule
Hauv ntu dhau los, peb twb tau kov ib feem ntawm cov ntsiab lus ntawm kev sib txuas lus ntawm monomers hauv DNA chains thiab hauv cov noob caj noob ces-mRNA complex. Tus naas ej biochemist E. Chargaff tau tsim ib qho khoom tshwj xeeb ntawm deoxyribonucleic acid molecules, uas yog hais tias tus naj npawb ntawm adenine nucleotides nyob rau hauv nws yeej ib txwm sib npaug rau thymine, thiab guanine - rau cytosine. Lub hauv paus ntsiab lus ntawm Chargaff lub hauv paus ntsiab lus yog kev tshawb fawb ntawm Watson thiab Crick, uas tsim cov monomers tsim DNA molecule thiab lub koom haum spatial lawv muaj dab tsi. Lwm tus qauv, muab los ntawm Chargaff thiab hu ua lub hauv paus ntsiab lus ntawm complementarity, qhia txog kev sib raug zoo ntawm purine thiab pyrimidine bases thiab lawv lub peev xwm los tsim hydrogen bonds thaum sib cuam tshuam nrog ib leeg. Qhov no txhais tau hais tias kev npaj ntawm monomers nyob rau hauv ob qho tib si DNA strands yog nruj me ntsis txiav txim: piv txwv li, opposite A ntawm thawj DNA strand yuav ua tau.tsuas yog T sib txawv thiab ob daim ntawv cog lus hydrogen tshwm sim ntawm lawv. Tawm tsam guanine nucleotide, tsuas yog cytosine tuaj yeem nyob. Hauv qhov no, peb daim ntawv cog lus hydrogen tsim ntawm cov hauv paus nitrogenous.
Lub luag haujlwm ntawm nucleotides hauv cov kab mob caj ces
Txhawm rau ua tiav cov tshuaj tiv thaiv ntawm cov protein biosynthesis tshwm sim hauv ribosomes, muaj cov txheej txheem rau kev hloov cov ntaub ntawv hais txog cov amino acid muaj pes tsawg leeg ntawm peptide los ntawm mRNA nucleotide sib lawv liag rau hauv cov amino acid sib lawv liag. Nws muab tawm tias peb lub monomers uas nyob ib sab nqa cov ntaub ntawv hais txog ib qho ntawm 20 cov amino acids tau. Qhov tshwm sim no hu ua genetic code. Hauv kev daws teeb meem hauv molecular biology, nws yog siv los txiav txim siab ob qho tib si amino acid muaj pes tsawg leeg ntawm peptide thiab kom meej cov lus nug: uas monomers tsim ib DNA molecule, nyob rau hauv lwm yam lus, dab tsi yog qhov muaj pes tsawg leeg ntawm cov noob sib raug. Piv txwv li, AAA triplet (codon) nyob rau hauv cov noob encodes cov amino acid phenylalanine nyob rau hauv cov protein molecule, thiab nyob rau hauv cov noob caj noob ces nws yuav sib haum mus rau lub UUU triplet nyob rau hauv lub mRNA saw.
Kev sib cuam tshuam ntawm nucleotides hauv cov txheej txheem ntawm DNA reduplication
Raws li nws tau pom ua ntej lawm, chav tsev, DNA monomers yog nucleotides. Lawv cov kab ke tshwj xeeb hauv cov chains yog cov qauv rau cov txheej txheem ntawm kev sib txuas ntawm tus ntxhais molecule ntawm deoxyribonucleic acid. Qhov tshwm sim no tshwm sim hauv S-theem ntawm cell interphase. Lub nucleotide ib theem zuj zus ntawm DNA molecule tshiab yog sib sau ua ke ntawm niam txiv chains nyob rau hauv qhov kev txiav txim ntawm DNA polymerase enzyme, coj mus rau hauv tus account lub hauv paus ntsiab lus.complementarity (A - T, D - C). Replication yog hais txog cov tshuaj tiv thaiv ntawm matrix synthesis. Qhov no txhais tau hais tias DNA monomers thiab lawv cov qauv nyob rau hauv niam txiv chains ua lub hauv paus, uas yog, matrix rau nws tus me nyuam daim ntawv.
Puas tau tus qauv ntawm kev hloov pauv nucleotide
Los ntawm txoj kev, cia peb hais tias deoxyribonucleic acid yog ib qho kev tiv thaiv zoo heev ntawm cov cell nucleus. Muaj cov lus piav qhia txog qhov no: cov ntaub ntawv keeb kwm khaws cia hauv chromatin ntawm lub nucleus yuav tsum tsis hloov pauv thiab luam tawm yam tsis muaj kev cuam tshuam. Zoo, cellular genome yog tas li "hauv qab phom" ntawm ib puag ncig yam. Piv txwv li, xws li aggressive chemical compounds xws li cawv, tshuaj, hluav taws xob hluav taws xob. Tag nrho cov ntawm lawv yog hu ua mutagens, nyob rau hauv tus ntawm cov DNA monomer hloov nws cov qauv tshuaj. Xws li ib tug distortion nyob rau hauv biochemistry yog hu ua ib tug point mutation. Qhov zaus ntawm lawv qhov tshwm sim hauv cov genome ntawm tes yog qhov siab heev. Kev hloov pauv tau raug kho los ntawm kev ua haujlwm zoo ntawm kev kho cellular, uas suav nrog cov enzymes.
Qee tus ntawm lawv, piv txwv li, txwv, "txiav tawm" cov nucleotides puas lawm, polymerases muab cov synthesis ntawm ib txwm monomers, ligases "sew" cov seem ntawm cov noob. Yog tias, vim li cas, cov txheej txheem uas tau piav qhia saum toj no tsis ua haujlwm hauv lub xovtooj ntawm tes thiab qhov tsis zoo DNA monomer tseem nyob hauv nws cov molecule, kev hloov pauv tau khaws los ntawm cov txheej txheem ntawm matrix synthesis thiab phenotypically manifests nws tus kheej nyob rau hauv daim ntawv ntawm cov proteins uas impaired zog. tsis tuaj yeem ua cov haujlwm tsim nyog muaj nyob hauv lawv hauvcellular metabolism. Qhov no yog ib qho tsis zoo uas yuav txo tau txoj sia nyob ntawm tes thiab ua rau nws lub neej luv.
