Selective nucleolus organizer inactivation in Arabidopsis is a chromosome position-effect phenomenon

Selective nucleolus organizer inactivation in Arabidopsis is a chromosome position-effect phenomenon.

Nucleolus organizer regions (NORs) are chromosomal loci where hundreds of rRNA genes are clustered. Despite being nearly identical in sequence, specific rRNA genes are selected for silencing during development via choice mechanism(s) that remain unclear. In Arabidopsis thaliana, rRNA gene subtypes that are silenced during development were recently mapped to the NOR on chromosome 2, NOR2, wherea...

Use of RFLPs larger than 100 kbp to map the position and internal organization of the nucleolus organizer region on chromosome 2 in Arabidopsis thaliana.

In Arabidopsis thaliana ribosomal RNA genes (rRNA genes or rDNA) are grouped in two nucleolus organizer regions(NORs) that together comprise approximately 6% of the genome. The map positions of the NORs relative to other genetic markers are unknown. It was found that the restriction endonuclease Hindlll cuts once in some but not all rRNA genes to yield strain-specific RFLPs of 100-700 kb that c...

X Chromosome Inactivation in Opioid Addicted Women

Introduction: X chromosome inactivation (XCI) is a process during which one of the two X chromosomes in female human is silenced leading to equal gene expression with males who have only one X chromosome. Here we have investigated XCI ratio in females with opioid addiction to see whether XCI skewness in women could be a risk factor for opioid addiction. Methods: 30 adult females meeting DS...

Ribosomal Rna in the Nucleolus Organizer

Interchanges in popcorn (Zea mays L.) involving the nucleolus organizer chromosome

The analysis of microsporogenesis in endogamous plants of popcorn (S5 to S7) showed several and distinct interchanges which involve the nucleolus organizer (chromosome 6). The detection of cells with interchanges was facilitated by the presence of two nucleoli of different sizes in contrast to normal ones with a single big nucleolus. Interchange points do not always seem to be at the same place...