Kab lus no yuav tham txog cov qauv ntawm eukaryotic hlwb li chromosomes, cov qauv thiab kev ua haujlwm uas tau kawm los ntawm ib ceg ntawm biology hu ua cytology.
Discovery keeb kwm
Ua cov khoom tseem ceeb ntawm cov cell nucleus, chromosomes tau pom nyob rau xyoo 19th los ntawm ntau tus kws tshawb fawb ib zaug. Lavxias teb sab biologist I. D. Chistyakov kawm lawv nyob rau hauv tus txheej txheem ntawm mitosis (cell division), German anatomist Waldeyer nrhiav tau lawv thaum lub sij hawm kev npaj ntawm histological npaj thiab hu ua lawv chromosomes, uas yog, staining lub cev rau cov tshuaj tiv thaiv sai ntawm cov qauv no thaum interacting nrog lub organic dye fuchsin.
Fleming tau sau cov lus tseeb ntawm kev tshawb fawb txog kev ua haujlwm ntawm chromosomes hauv cov hlwb nrog tsim cov nucleus.
qauv sab nraud ntawm chromosomes
Cov kab mob microscopic no nyob rau hauv lub nuclei - cov organelles tseem ceeb tshaj plaws ntawm cov cell, thiab ua qhov chaw khaws cia thiab xa cov ntaub ntawv keeb kwm ntawm ib lub cev. Chromosomesmuaj cov khoom tshwj xeeb - chromatin. Nws yog ib tug conglomerate ntawm nyias filaments - fibrils thiab granules. Los ntawm kev pom tshuaj lom neeg, qhov no yog kev sib xyaw ntawm cov kab DNA molecules (muaj li 40%) nrog cov protein tshwj xeeb histone.
Complexes, uas suav nrog 8 peptide molecules thiab DNA strands, twisted ntawm protein globules, zoo li ntawm coils, hu ua nucleosomes. Lub cheeb tsam deoxyribonucleic acid tsim 1.75 tig ib ncig ntawm cov qia thiab yog ib qho ellipsoid li ntawm 10 nanometers ntev thiab 5-6 dav. Lub xub ntiag ntawm cov qauv no (chromosomes) nyob rau hauv lub nucleus yog ib tug systematic feature ntawm lub hlwb ntawm eukaryotic kab mob. Nws yog nyob rau hauv daim ntawv ntawm nucleosomes uas chromosomes ua lub luag haujlwm ntawm kev khaws cia thiab xa tag nrho cov caj ces zoo.
Kev nyob ntawm tus qauv ntawm chromosome nyob rau theem ntawm lub voj voog ntawm tes
Yog hais tias ib lub xovtooj nyob rau hauv lub xeev ntawm interphase, uas yog yus muaj los ntawm nws txoj kev loj hlob thiab intensive metabolism, tab sis tsis muaj kev faib, ces cov chromosomes nyob rau hauv lub nucleus zoo li nyias despiralized threads - chromonemes. Feem ntau lawv yog intertwined, thiab nws yog tsis yooj yim sua kom visually cais lawv mus rau hauv nyias cov qauv. Thaum lub sij hawm ntawm kev faib cell, uas yog hu ua mitosis nyob rau hauv somatic hlwb, thiab meiosis nyob rau hauv kev sib deev hlwb, cov chromosomes pib mus kauv thiab thicken, ua kom pom tseeb nyob rau hauv ib lub microscope.
Levels of chromosome organization
Cov chav nyob ntawm kev xeeb tub yog chromosomes, kev tshawb fawb ntawm kev tshawb fawb txog noob caj noob ces kom meej. Cov kws tshawb fawb tau pom tias cov nucleosomal filament,muaj DNA thiab histone proteins tsim ib qho kev txiav txim thawj zaug. Cov ntim ntom ntom ntawm chromatin tshwm sim vim yog tsim cov qauv kev txiav txim siab dua - solenoid. Nws tus kheej-organizes thiab condenses rau hauv ib qho nyuaj heev supercoil. Tag nrho cov theem saum toj no ntawm lub koom haum chromosome tshwm sim thaum lub sij hawm npaj ntawm tes rau kev faib.
Nws yog nyob rau hauv lub voj voog mitotic uas cov txheej txheem ntawm kev sib hloov, uas muaj cov noob uas muaj DNA, luv luv thiab thickened piv rau cov filamentous chromonemes ntawm lub sij hawm interphase txog li 19 txhiab zaus. Nyob rau hauv xws li ib tug compact daim ntawv, cov chromosomes ntawm lub nucleus, uas nws lub luag hauj lwm yog kis tau tus yam ntxwv hereditary ntawm lub cev, npaj txhij rau kev faib ntawm somatic los yog kab mob hlwb.
YChromosome morphology
Cov haujlwm ntawm chromosomes tuaj yeem piav qhia los ntawm kev kawm txog lawv cov yam ntxwv morphological, uas pom zoo tshaj plaws hauv lub voj voog mitotic. Nws tau raug pov thawj tias txawm tias nyob rau hauv theem hluavtaws ntawm interphase, qhov loj ntawm DNA hauv lub xov tooj ntawm tes ob npaug, txij li txhua tus ntxhais lub hlwb tsim los ntawm kev faib yuav tsum muaj cov ntaub ntawv keeb kwm tib yam li tus niam thawj. Qhov no tau ua tiav los ntawm cov txheej txheem ntawm kev rov ua dua tshiab - tus kheej-ob npaug ntawm DNA, uas tshwm sim nrog kev koom tes ntawm enzyme DNA polymerase.
Hauv kev npaj cytological npaj thaum lub sijhawm metaphase ntawm mitosis, hauv cov nroj tsuag lossis tsiaj cov hlwb hauv lub tshuab ntsuas, nws pom tseeb tias txhua chromosome muaj ob ntu, hu uachromatids. Nyob rau theem ntxiv ntawm mitosis - anaphase thiab, tshwj xeeb tshaj yog, telophase - lawv tau sib cais tag nrho, vim tias txhua tus chromatid dhau los ua cov chromosome cais. Nws muaj qhov txuas txuas ntxiv DNA molecule, nrog rau lipids, acidic proteins thiab RNA. Ntawm cov ntxhia tshuaj, nws muaj magnesium thiab calcium ions.
Pab cov khoom tsim ntawm chromosome
txhawm rau txhawm rau ua haujlwm ntawm chromosomes hauv lub xov tooj ntawm tes kom ua tiav tag nrho, cov kab ke ntawm kev xeeb tub no muaj cov cuab yeej tshwj xeeb - thawj constriction (centromere), uas tsis muaj spiralizes. Nws yog nws uas faib cov chromosome ua ob ntu, hu ua lub xub pwg nyom. Nyob ntawm qhov chaw ntawm lub centromere, geneticists faib chromosomes raws li sib npaug-armed (metacentric), tsis sib npaug-armed (submetacentric) thiab acrocentric. Ntawm cov thawj constrictions, tshwj xeeb formations yog tsim - kinetochores, uas yog disc-zoo li tus protein globules nyob rau ntawm ob sab ntawm lub centromere. Cov kinetochore lawv tus kheej muaj ob ntu: sab nraud yog nyob rau hauv kev sib cuag nrog microfilaments (filament spindle threads), txuas rau lawv.
Vim qhov txo qis ntawm cov filaments (microfilaments), kev txiav txim ncaj qha ntawm cov chromatids uas ua rau cov chromosome ntawm cov ntxhais cell raug ua. Qee cov chromosomes muaj ib lossis ntau qhov kev txwv thib ob uas tsis koom nrog hauv mitosis, vim fission spindle threads tsis tuaj yeem txuas rau lawv, tab sis nws yog cov ntu no (thib ob constrictions) uas muab kev tswj hwm ntawm cov synthesis ntawm nucleoli - organelles uas teb.rau kev tsim ntawm ribosomes.
Dab tsi yog karyotype
Cov kws tshawb fawb caj ces paub zoo Morgan, N. Koltsov, Setton thaum pib ntawm lub xyoo pua 20th scrupulously kawm chromosomes, lawv cov qauv thiab kev ua haujlwm hauv cov hlwb somatic thiab cov kab mob - gametes. Lawv pom tias txhua lub xov tooj ntawm txhua hom kab mob lom neeg yog tus cwj pwm los ntawm qee tus lej ntawm chromosomes uas muaj cov duab tshwj xeeb thiab loj. Nws tau thov kom hu tag nrho cov chromosomes nyob rau hauv lub nucleus ntawm somatic cell ib karyotype.
Hauv cov ntaub ntawv nrov, karyotype feem ntau txheeb xyuas nrog cov chromosome teeb. Qhov tseeb, cov no tsis yog cov tswv yim zoo ib yam. Piv txwv li, nyob rau hauv tib neeg, karyotype yog 46 chromosomes nyob rau hauv lub nuclei ntawm somatic hlwb thiab yog denoted los ntawm cov mis 2n. Tab sis xws li cov hlwb xws li, piv txwv li, hepatocytes (lub siab hlwb) muaj ob peb lub nuclei, lawv cov chromosome teeb tsa yog 2n2=4n lossis 2n4=8n. Ntawd yog, tus lej ntawm chromosomes hauv cov hlwb no yuav ntau dua 46, txawm hais tias karyotype ntawm hepatocytes yog 2n, uas yog, 46 chromosomes.
Tus naj npawb ntawm cov chromosomes hauv cov kab mob ib txwm muaj ob zaug tsawg dua li hauv somatic (hauv cov hlwb ntawm lub cev), xws li cov txheej txheem hu ua haploid thiab yog denoted li n. Tag nrho lwm cov hlwb hauv lub cev muaj ib txheej ntawm 2n, uas yog hu ua diploid.
Morgan's chromosome theory of heredity
American geneticist Morgan nrhiav tau txoj cai ntawm kev sib txuas ntawm cov noob caj noob ces, ua kev sim ntawm kev sib xyaw ntawm cov txiv hmab txiv ntoo yoov-Drosophila. Ua tsaug rau nws txoj kev tshawb fawb, kev ua haujlwm ntawm chromosomes ntawm cov kab mob hlwb tau kawm. Morgan tau ua pov thawj tias cov noob nyob hauv cov neeg nyob sib zeloci ntawm tib chromosome tau txais txiaj ntsig feem ntau ua ke, uas yog, txuas. Yog tias cov noob nyob deb sib nrug ntawm cov chromosome, ces hla dhau ntawm tus viv ncaus chromosomes - kev sib pauv ntawm ntu.
Ua tsaug rau Morgan txoj kev tshawb fawb, daim ntawv qhia caj ces tau tsim los kawm txog kev ua haujlwm ntawm chromosomes thiab tau siv dav hauv kev sib tham txog caj ces los daws cov lus nug txog kev muaj peev xwm ntawm cov chromosomes lossis cov noob uas ua rau muaj kab mob hauv tib neeg. Qhov tseem ceeb ntawm cov lus xaus los ntawm tus kws tshawb fawb tsis tuaj yeem kwv yees ntau dhau.
Nyob rau hauv kab lus no, peb tshuaj xyuas cov qauv thiab kev ua haujlwm ntawm chromosomes uas lawv ua nyob rau hauv lub cell.
