Qhov sib txawv tseem ceeb ntawm kev sim hla thiab rov qab yog qhov kev sim hla yog tus ntoo khaub lig uas tshwm sim ntawm qhov tseem ceeb phenotype thiab cov phenotype recessive thaum lub backcross yog tus ntoo khaub lig uas tshwm sim ntawm tiam F1 hybrid thiab ib tug ntawm ob niam txiv.
Kev nkag siab qhov sib txawv ntawm kev sim hla thiab rov qab yog qhov tseem ceeb hauv cov noob caj noob ces vim tias lawv yog ob hom ntoo khaub lig uas muaj txiaj ntsig zoo los txheeb xyuas cov genotype ntawm tus tsiaj lossis cov nroj tsuag. Lub hom phiaj tseem ceeb ntawm kev ua qhov kev xeem tus ntoo khaub lig thiab backcross yog nrhiav cov heterozygosity lossis homozygosity ntawm tib neeg los ntawm kev txheeb xyuas cov hom gametes uas tsim cov genotypes tseem ceeb.
Xav txog qhov piv txwv hauv qab no kom nkag siab ob qho tib si ntoo khaub lig thiab qhov sib txawv ntawm kev sim hla thiab rov qab. Ntawm no, 'T' qhia txog qhov tseem ceeb ntawm cov txiv ntoo siab siab, thiab 't' qhia txog qhov tsis zoo ntawm tib lub phenotype. Ib tsob txiv ntoo siab siab tuaj yeem muaj nyob hauv homozygous (TT) lossis heterozygous (Tt) thiab cov nroj tsuag dwarf hybrid yeej ib txwm homozygous recessive (tt).
Test Cross yog dab tsi?
Nyob rau hauv kev xeem hla, F1 hybrid hla rov qab nrog niam txiv recessive. Hauv lwm lo lus, kev sim hla yog tus ntoo khaub lig ntawm qhov tseem ceeb phenotype (TT lossis Tt) thiab homozygous recessive (tt). Mendel yog thawj tus neeg ua tus ntoo khaub lig kuaj xyuas seb tus neeg puas yog heterozygous lossis homozygous rau tus cwj pwm tseem ceeb. Lwm yam tshaj li kev tshawb pom heterozygosity, kev sim hla kuj tseem muaj txiaj ntsig los kuaj xyuas qhov purity ntawm gametes tsim los ntawm niam txiv.
Yog tias homozygous dominant F1 hybrid (TT) hla nrog cov niam txiv recessive, nws yeej yuav ua rau 100% heterozygous siab hybrids. Daim duab hauv qab no piav qhia qhov no.
Yog tias qhov sib txawv tseem ceeb F1 hybrid (Tt) hla nrog cov niam txiv recessive, tsuas yog 50% yuav siab, thiab 50% yuav dwarf. Daim duab hauv qab no piav qhia qhov no.
Dab tsi yog Backcross?
Nyob rau hauv backcross, F1 hybrid hla rov qab nrog ib tus niam txiv, txawm tias tseem ceeb lossis rov qab. Backcrosses nce cov txiaj ntsig zoo hauv cov neeg. Piv txwv li, qee cov qoob loo cog hybrids rov qab nrog cov tsiaj qus kom rov qab tau lawv cov txiaj ntsig zoo xws li kev tiv thaiv kab mob, cov txiaj ntsig siab, thiab lwm yam.
Daim duab 03: Rov qab
Txawm li cas los xij, cov txheej txheem no tuaj yeem ua rau lwm cov txiaj ntsig zoo ntawm kev sib xyaw. Yuav kom kov yeej qhov kev tsis zoo no, cov hybrids tau rov qab rov qab dua nrog nws cov niam txiv cov nroj tsuag dhau ob peb tiam kom tau txais lawv cov txiaj ntsig zoo rov qab rau hauv cov hybrids tshiab.
Dab tsi zoo sib xws ntawm Kev Xeem Hla thiab Backcross?
- Kev ntsuas tus ntoo khaub lig thiab rov qab muaj txiaj ntsig zoo hauv kev cog qoob loo thiab tsiaj txhu.
- Lawv piav qhia txog phenotypes thiab genotypes ntawm cov kab mob thiab seb lawv dhau mus rau tiam tom ntej.
- Txhua qhov kev xeem hla yog rov qab.
- Lawv txiav txim siab txog genotype ntawm ib tus neeg thiab pab kom rov qab tau cov yam ntxwv tseem ceeb.
- Nyob rau hauv ob qho tib si, kev hla yog ntawm cov genotypes tsis paub.
Qhov txawv ntawm Kev Xeem Hla thiab Backcross yog dab tsi?
Test crosses thiab backcross yog ob hom ntoo khaub lig nrov hauv kev cog qoob loo. Kev sim hla tshwm sim ntawm qhov tseem ceeb phenotype nrog cov phenotype recessive los txiav txim qhov genotype ntawm cov phenotype tseem ceeb. Backcross pab kom rov qab tau cov cim tseem ceeb ntawm cov niam txiv pej xeem nyob rau hauv hybrid pejxeem.
Summary – Test Cross vs Backcross
Txhua qhov kev xeem hla yog ib hom kev rov qab, tab sis tag nrho cov hla rov qab tsis yog tus ntoo khaub lig. Thaum lub sij hawm backcross, tus hla rov qab ntawm F1 hybrid yog nrog ib tug ntawm cov niam txiv, xws li homozygous los yog heterozygous. Txawm li cas los xij, thaum lub sij hawm sim hla, hla rov qab ntawm F1 hybrid yog ib txwm nrog cov niam txiv recessive. Ib qho kev sim hla yog qhov tseem ceeb los txiav txim siab txog genotype (TT lossis Tt) ntawm qhov tseem ceeb phenotype thaum backcross muaj txiaj ntsig zoo hauv kev rov ua kom cov yam ntxwv tseem ceeb ntawm niam txiv. Qhov no yog qhov txawv ntawm qhov kev sim hla thiab rov qab.
