cariotipuri si bandari cromozomale_2011
TRANSCRIPT
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Cariotip uman normal, 46,XX sau 46, XY
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Cromozomi de la om: 46, XX- cariotip spectral
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Trisomia 21= sindromul Down= 47, XY, +21= exista un cromozom 21 in plus (o trisomie);
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Fenotipuri- sindrom Down
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Intr-o translocatie reciproca , anumite parti din cromozomi sunt rearanjate, astfel incat nici nu se castiga si nici nu se pierde material genetic. Unele cazuri de sindrom Down sunt
determinate de translocatiea14/21- aceste cazuri de sindrom se mostenesc!
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Monosomie= sindromul Turner= 45,X = lipseste un cromozom, si anume: unul dintre cromozomii de sex, X. Se intalneste numai la femei, compatibil cu viata.
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Sindrom Turner= monosomia X= 2n=44, X0, caracteristici fenotipice
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Poliploidia = prezenta mai multor seturi (n) de cromozomi. Haploid = n = numarul perechilor de cromozomi. Cele mai multe dintre organisme sunt diploide, 2n, si gametii lor sunt haploizi, n. Pot apare si organisme 3n (triploid) si 4n (tetraploid). spre deosebire de Aneuploidie, care se refera la variatia numarului de cromozomi din perechi, unul dintre cromozomi e in plus sau in minus.
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Mozaicismul se noteaza “/",De ex., 45, X / 46, XX indica o femela Turner avand doua linii celulare , una normala si una cu un cromozom X lipsa. Poate sa apara din nondisjunctie post zigotica, si in mitoza zigotului sau a embrionului .
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SCE, Sister Chromatid Exchange (stanga- normal; dreapta= sindromul Bloom)SCE este utilizat pentru diagnosticul sindr. Bloom, o boala genetica care consta in multiple rupturi cromozomale . SCE este si un test pentru mutagenicitate (ex. E-uri din alimentatie).
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Cariotip patologic
Bandare G si C
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Ex.de Repere care diferentiaza pozitia citologica a unei regiuni dintr-un cromozom (centromer, telomer, brat scurt (p) si lung (q), regiuni, benzi si subbenzi- la cromozomii in prometafaza). Nu exista interbenzi.Patternul de bandare nu e natural, e indus chimic!