Txoj kev sib tw vs kev sib koom ua ke
Nruab nrab ntawm Kev Sib Txuas thiab Kev Sib Koom Tes peb tuaj yeem txheeb xyuas qee qhov sib txawv vim lawv yog ob lub ntsiab lus sib txawv ntsig txog caj ces. Yog li ntawd, lawv yuav tsum tsis txhob totaub. Qhov tseeb, kev sib txuas piav qhia txog qhov tshwm sim ntawm cov noob ntawm tib chromosome thiab kev sib koom ua ke piav qhia txog kev sib xyaw ntawm cov noob ntawm homologous chromosomes thaum lub sij hawm meiosis ntawm tus txheej txheem hu ua hla.
Txoj kev sib txuas yog dab tsi?
Cov noob uas nyob ze ua ke hauv tib chromosome yog lub npe hu ua cov noob caj noob ces. Txij li thaum lawv nyob ze rau ib leeg thiab nyob hauv tib chromosome, lawv hu ua pawg sib txuas thiab zoo li qub ua ke ua ib chav tsev thaum meiosis ntawm cell division. Qhov ntawd yog cov noob caj noob ces tsis ua raws li Mendel lub hauv paus ntsiab lus ntawm kev ywj pheej assortment (ob lub alleles nyob ntawm ib qho chaw / qhov chaw cais (segregate) rau hauv ob lub hlwb ntawm nws tus kheej los ntawm lwm cov alleles ntawm lwm loci).
Txuas tuaj yeem muab faib ua ob hom:
Txoj kev sib txuas - thaum cov noob nyob ze ze ua ke thiab tsis pom kev hla dhau, nws paub tias yog kev sib txuas ua tiav. Qhov no ua rau cov poj niam uas tsis yog recombinant. Qhov ntawd yog phenotype thiab genotype ntawm cov nroj tsuag progeny zoo ib yam li lawv niam cov nroj tsuag.
Kev sib txuas tsis tiav - thaum cov noob nyob hauv tib chromosome thiab qhia qee qhov kev hla thaum meiosis tau hais tias yog cov noob tsis tiav. Kev sim rau kev sib txuas tsis tiav tuaj yeem ua tiav los ntawm kev siv testcross. Piv txwv li, ib tsob nroj uas yog heterozygous rau ob lub cim yuav tsum tau hla nrog cov nroj tsuag uas yog recessive rau tus cwj pwm ntawd. Hom ntoo khaub lig no ua rau ob lub gametes recombinant thiab ob lub gametes uas tsis yog recombinant. E.g. qauv baldness hauv cov txiv neej txuas nrog cov cim caj ces hauv X chromosome thiab xim ntawm lub thorax thiab cov puparium ntawm Australian blowfly Luciliácuprina.
piv txwv Baldness for Incomplete linkage
Raws li cas alleles ntawm cov noob caj noob ces nyob ntawm homologous chromosomes, muaj ob hom kev teeb tsa raws li hauv qab no:
Kev sib txuas (Cis) kev teeb tsa - qhov xwm txheej uas ob qho tseem ceeb alleles nyob ntawm ib chromosome thiab ob lub recessive alleles nyob rau lwm chromosome.
Repulsion (Trans) configuration - qhov xwm txheej uas txhua chromosome muaj ib qho tseem ceeb thiab ib qho allele recessive.
Kev sib koom ua ke yog dab tsi?
Cov noob uas nyob hauv tib chromosome tuaj yeem hloov pauv ntawm ib qho chromosome homologous mus rau lwm qhov ntawm cov txheej txheem hu ua hla. Nws ua rau cov chromosomes nrog cov noob tshiab sib xyaw ua ke piv rau lawv cov niam cell gene arrangement (daim duab 2). Yog li ntawd, chromosomes nrog cov noob tshiab no ua ke hu ua recombinant chromosomes thiab yog li cov txheej txheem hu ua recombination.
Crossover tsim cov khoom sib txuas
Feem pua ntawm cov recombinants tsim nyob rau hauv tus ntoo khaub lig yog hu ua recombination zaus, qhov no yuav xam tau raws li nram no:
Recombination zaus=(Number of recombinant in the progeny) / (Tag nrho tus naj npawb hauv progeny) 100 %
Muaj ob hom kev sib txuas ua ke uas tuaj yeem tshwm sim thaum lub sijhawm meiosis:
Interchromosomal recombination - recombination tshwm sim ntawm cov noob nyob rau ntawm cov chromosomes sib txawv. E.g. Kev ywj pheej assortment ntawm anaphase ntawm meiosis I.
Intrachromosomal recombination - recombination tshwm sim ntawm cov noob nyob rau tib chromosome. E.g. hla dhau ntawm prophase ntawm meiosis I.
Thaum recombination tshwm sim nyob rau hauv cov noob txuas, ua rau progeny tshwm sim feem ntau ntawm cov tsis-recombinants thiab tsawg zaus ntawm recombinants.
Dab tsi yog qhov sib txawv ntawm Kev Sib Txuas thiab Kev Sib Koom Tes?
• Linkage pab khaws qee cov noob ua ke hauv tib lub chromosome whereas, txheej txheem ntawm recombination mix noob ntawm chromosomes.
• Kev sib txuas yog qhov tshwm sim uas tuaj yeem pom hauv txhua hom ntawm tes. Txawm li cas los xij, recombination yog ib qho txheej txheem uas tshwm sim thaum meiosis I.
• Recombination tsis tshwm sim thaum muaj kev sib txuas ua tiav. Txawm li cas los xij, recombination tshwm sim thaum cov noob tsis txuas tag nrho (lossis thaum lawv txuas tsis tiav).
• Cov noob txuas tsis tiav tau txais kev sib txuas ntawm intrachromosomal.
• Thaum recombination tshwm sim nyob rau hauv nws tus kheej assorting noob, recombinants thiab non-recombinants tshwm sim nyob rau hauv sib npaug proportions whereas, thaum recombination tshwm sim nyob rau hauv tsis tiav txuas cov noob recombinant zaus tsawg dua 50% thiab non-recombinant zaus yog ntau tshaj 50%.
• Ob qhov kev sib txuas thiab kev sib koom ua ke tuaj yeem siv los tsim cov ntawv qhia caj ces / kev txheeb xyuas kev sib txuas (cov duab qhia chaw uas muaj cov noob caj noob ces).
Images Courtesy:.
- Pattern baldness in men by Welshsk (CC BY 3.0)
- Cross over produce recombinants by Jeffrey Mahr (CC BY 4.0)
