Cov kab mob caj ces, qhia hauv codons, yog ib qho system rau encoding cov ntaub ntawv hais txog cov qauv ntawm cov proteins, muaj nyob rau hauv tag nrho cov kab mob nyob hauv lub ntiaj teb. Nws decoding siv ib xyoo caum, tab sis qhov tseeb hais tias nws muaj, science to taub yuav luag ib puas xyoo. Universality, tshwj xeeb, unidirectionality, thiab tshwj xeeb tshaj yog degeneracy ntawm cov noob caj noob ces yog ib qho tseem ceeb heev lom zem.
Discovery keeb kwm
Qhov teeb meem ntawm kev sau cov ntaub ntawv caj ces ib txwm yog qhov tseem ceeb hauv biology. Kev tshawb fawb tau maj mam txav mus rau cov qauv matrix ntawm txoj cai caj ces. Txij li thaum qhov kev tshawb pom los ntawm J. Watson thiab F. Crick nyob rau hauv 1953 ntawm ob helical qauv ntawm DNA, lub theem ntawm unraveling lub heev qauv ntawm cov cai pib, uas prompted txoj kev ntseeg nyob rau hauv lub greatness ntawm xwm. Cov qauv linear ntawm cov proteins thiab tib cov qauv ntawm DNA qhia tias muaj cov kab mob caj ces raws li kev sau ntawv ntawm ob phau ntawv, tab sis sau siv cov tsiaj ntawv sib txawv. Thiab yog tiasCov tsiaj ntawv ntawm cov protein tau paub, tom qab ntawd cov cim ntawm DNA tau los ua kev kawm rau biologists, physicists thiab lej.
Nws ua rau tsis muaj kev nkag siab los piav qhia txhua kauj ruam hauv kev daws qhov kev sib cav no. Ib qho kev sim ncaj qha, uas tau ua pov thawj thiab lees paub tias muaj kev sib raug zoo ntawm DNA codons thiab protein amino acids, tau ua nyob rau xyoo 1964 los ntawm C. Janowski thiab S. Brenner. Thiab ces - lub sij hawm ntawm deciphering cov noob caj noob ces nyob rau hauv vitro (hauv vitro) siv cov tswv yim ntawm protein synthesis nyob rau hauv cell-dawb qauv.
Qhov kev txiav txim siab tag nrho E. coli tau tshaj tawm rau pej xeem hauv xyoo 1966 ntawm kev sib tham ntawm cov kws kho tsiaj hauv Cold Spring Harbor (USA). Tom qab ntawd qhov redundancy (degeneracy) ntawm cov noob caj noob ces tau pom. Qhov no txhais tau li cas tau piav qhia yooj yim heev.
Kev txiav txim txuas ntxiv
Tau txais cov ntaub ntawv ntawm kev txiav txim siab ntawm cov txheej txheem keeb kwm tau dhau los ua ib qho xwm txheej tseem ceeb tshaj plaws ntawm lub xyoo pua xeem. Niaj hnub no, kev tshawb fawb txuas ntxiv mus kawm nyob rau hauv qhov tob ntawm cov txheej txheem ntawm molecular encodings thiab nws cov yam ntxwv ntawm cov txheej txheem thiab ntau dhau ntawm cov paib, uas qhia txog cov khoom ntawm degeneracy ntawm cov caj ces. Ib ceg ntawm kev kawm yog qhov tshwm sim thiab kev hloov pauv ntawm cov txheej txheem coding rau cov khoom qub. Cov ntaub ntawv pov thawj ntawm kev sib raug zoo ntawm polynucleotides (DNA) thiab polypeptides (proteins) tau muab lub zog rau txoj kev loj hlob ntawm molecular biology. Thiab qhov ntawd, dhau los, mus rau biotechnology, bioengineering, nrhiav pom hauv kev xaiv thiab qoob loo ntau lawm.
Dogmas thiab cov cai
Lub ntsiab dogma ntawm molecular biology - cov ntaub ntawv raug pauv los ntawm DNA mus rau cov ntaub ntawvRNA, thiab tom qab ntawd los ntawm nws mus rau cov protein. Nyob rau hauv qhov opposite direction, kis tau los ntawm RNA rau DNA thiab los ntawm RNA mus rau lwm RNA.
Tab sis lub matrix lossis lub hauv paus yog ib txwm DNA. Thiab tag nrho lwm cov yam ntxwv tseem ceeb ntawm kev sib kis ntawm cov ntaub ntawv yog ib qho kev xav ntawm no matrix xwm ntawm kev sib kis. Namely, kev hloov pauv los ntawm kev sib txuas ntawm cov matrix ntawm lwm cov molecules, uas yuav dhau los ua cov qauv ntawm kev tsim tawm ntawm cov ntaub ntawv keeb kwm.
Genetic code
Linear coding ntawm cov qauv ntawm cov protein molecules yog ua los ntawm kev siv cov codons (triples) ntawm nucleotides, ntawm uas tsuas muaj 4 (adeine, guanine, cytosine, thymine (uracil)), uas spontaneously ua rau kev tsim. ntawm lwm cov saw ntawm nucleotides. Tib tus lej thiab tshuaj lom neeg ntxiv ntawm nucleotides yog lub ntsiab lus tseem ceeb rau kev sib xyaw ua ke. Tab sis thaum lub sij hawm tsim cov protein molecule, tsis muaj kev sib tham ntawm qhov ntau thiab zoo ntawm monomers (DNA nucleotides yog protein amino acids). Qhov no yog qhov kev cai lij choj ntawm ntuj tsim - ib qho kev kaw lus nyob rau hauv cov kab ke ntawm nucleotides (codons) cov kab ke ntawm cov amino acids hauv cov protein.
Tus kab mob caj ces muaj ntau yam khoom:
- Uniqueness.
- Kev qhia.
- Tsis sib npaug.
- Redundancy (degeneracy) ntawm txoj cai caj ces.
- Versatility.
Cia piav qhia luv luv, tsom mus rau qhov tseem ceeb ntawm kev lom neeg.
Tripletity, txuas ntxiv thiab nres
Txhua ntawm 61 amino acids sib raug rau ib qho kev sib txuas lus (triple) ntawm nucleotides. Peb triplets tsis nqa cov ntaub ntawv hais txog cov amino acid thiab nres codons. Txhua nucleotide nyob rau hauv cov saw yog ib feem ntawm ib tug triplet, thiab tsis muaj nyob rau ntawm nws tus kheej. Thaum kawg thiab thaum pib ntawm cov saw ntawm nucleotides lub luag haujlwm rau ib qho protein, muaj cov codons nres. Lawv pib lossis nres kev txhais lus (kev sib txuas ntawm cov protein molecule).
Tshwj xeeb, tsis sib tshooj thiab unidirectional
Txhua tus codon (triplet) cov lej tsuas yog ib qho amino acid xwb. Txhua triplet yog ywj siab ntawm tus neeg nyob sib ze thiab tsis sib tshooj. Ib qho nucleotide tuaj yeem suav nrog tsuas yog ib qho triplet hauv cov saw hlau. Protein synthesis ib txwm mus nyob rau hauv ib qho kev taw qhia, uas yog tswj los ntawm nres codons.
Redundancies of the genetic code
Txhua triplet ntawm nucleotides encodes ib amino acid. Muaj 64 nucleotides nyob rau hauv tag nrho, ntawm uas 61 encode amino acids (sense codons), thiab peb tsis muaj qab hau, uas yog, lawv tsis encode ib amino acid (stop codons). Lub redundancy (degeneracy) ntawm cov noob caj noob ces nyob rau hauv qhov tseeb hais tias nyob rau hauv txhua txhua triplet hloov yuav ua tau - radical (ua rau amino acid hloov) thiab conservative (tsis txhob hloov cov amino acid chav kawm). Nws yog ib qho yooj yim los xam tias yog tias 9 hloov pauv tuaj yeem ua rau hauv triplet (txoj haujlwm 1, 2 thiab 3), txhua nucleotide tuaj yeem hloov tau los ntawm 4 - 1=3 lwm txoj kev, ces tag nrho cov kev xaiv nucleotide hloov pauv yuav yog 61. x 9=549.
Qhov degeneracy ntawm txoj cai caj ces yog tshwm sim nyob rau hauv qhov tseeb tias 549 variants muaj ntau duatsim nyog rau encode cov ntaub ntawv hais txog 21 amino acids. Nyob rau tib lub sijhawm, tawm ntawm 549 qhov sib txawv, 23 qhov kev hloov pauv yuav ua rau tsim cov codons nres, 134 + 230 kev hloov pauv yog kev saib xyuas, thiab 162 kev hloov pauv yog radical.
Txoj cai ntawm degeneracy thiab cais tawm
Yog tias ob lub codons muaj ob qhov zoo tib yam thawj nucleotides, thiab tus so yog nucleotides ntawm tib chav kawm (purine lossis pyrimidine), ces lawv nqa cov ntaub ntawv hais txog tib cov amino acid. Qhov no yog txoj cai ntawm degeneracy los yog redundancy ntawm cov noob caj noob ces. Ob qhov kev zam - AUA thiab UGA - thawj encodes methionine, txawm hais tias nws yuav tsum yog isoleucine, thiab qhov thib ob yog nres codon, txawm hais tias nws yuav tsum tau encode tryptophan.
Lub ntsiab lus ntawm degeneracy thiab universality
Nws yog ob yam khoom ntawm cov noob caj noob ces uas muaj qhov tseem ceeb tshaj plaws lom neeg. Tag nrho cov khoom teev saum toj no yog cov yam ntxwv ntawm cov ntaub ntawv keeb kwm ntawm txhua hom kab mob nyob hauv peb lub ntiaj teb.
Lub degeneracy ntawm cov noob caj noob ces muaj tus nqi hloov pauv, zoo li ntau qhov sib npaug ntawm cov lej ntawm ib qho amino acid. Tsis tas li ntawd, qhov no txhais tau tias txo qis qhov tseem ceeb (degeneracy) ntawm peb nucleotide hauv codon. Qhov kev xaiv no txo qis kev hloov pauv hauv DNA, uas yuav ua rau muaj kev ua txhaum loj hauv cov qauv protein. Nov yog kev tiv thaiv kev tiv thaiv ntawm cov kab mob nyob hauv lub ntiaj teb.
