Data/hora: 22/09/2024 16:48:22

Biblioteca(s): 	Embrapa Gado de Leite.	
Data corrente: 	22/04/2019	
Data da última atualização: 	24/01/2023	
Autoria: 	ROCHA, L. C.; FERREIRA, M. T. M.; CUNHA, I. M. F.; MITTELMANN, A.; TECHIO, V. H.	
Afiliação: 	Laiane Corsini Rocha, UFLA; Marco Túlio Mendes Ferreira, UFLA; Isabela Martinez Fontes Cunha, UFLA; ANDREA MITTELMANN, CNPGL; Vânia Helena Techio, UFLA.	
Título: 	45S rDNA sites in meiosis of Lolium multiflorum Lam.: variability, non-homologous associations and lack of fragility.	
Ano de publicação: 	2019	
Fonte/Imprenta: 	Protoplasma, v. 256, n. 1, p. 227-235, 2019.	
Idioma: 	Inglês	
Conteúdo: 	Abstract In this study, we evaluated the behavior of 45S ribosomal DNA (rDNA) sites during the meiosis of Lolium multiflorum. The reason to study it in this species is that 45S rDNA sites are usually visualized as gaps in mitotic metaphase chromosomes and were initially denominated fragile sites (FSs). In different species, FSs were related to rearrangements that alter the karyotype and affect the chromosome pairing in meiosis. However, our findings show that the chromosome pairing in L. multiflorum is regular and, as in mitosis, the number of sites is variable. In diakinesis with five sites, one of the bivalents was in hemizygous state while, in diakinesis with seven sites, one of the bivalents had three conspicuous signals, two in syntheny in one of the homologous. Only four cells had gaps in the region of the 45S rDNA. Owing to the lower number of signals observed at the initial stages of meiosis, it is assumed that they are involved both in homologous and non-homologous associations and that they might assist the chromosome pairing. Regarding segregation, only meiocytes with five and six 45S rDNA signals were observed, and they were characterized by the segregation of 2/3 signals in the poles of anaphases I up to metaphases II; 2/2 and 3/3 in anaphases II and telophases II; and also 2/2 and 4/4 in the nuclei of tetrads, unlike the number of 45S signals expected. The numerical nonequivalence of sites among nuclei at later stages of meiosis is explained by the presence of chromosomes with hemizygous sites.	
Palavras-Chave: 	Fragile sites; Hemizygosis; Syntheny of rDNA genes.	
Thesaurus Nal: 	Chromosome segregation; Forage grasses.	
Categoria do assunto: 	F Plantas e Produtos de Origem Vegetal	
Registro original: 	Embrapa Gado de Leite (CNPGL)	
Exemplares: 	CNPGL - (24618-1) - UPC - AP - DD -  -  -  - DIS