title: Ribosomal RNA, maternal age, and Down's syndrome.
abstract: A selective loss (or a blocking) of rRNA genes in ageing oocytes, and its compensation through the retention of an acrocentric nucleolar organizer chromosome, is proposed as a possible mechanism responsible for the increased frequency of Down's syndrome with maternal age.
mesh_terms: D000818:Animals; D001001:Anura; D004314:Down Syndrome / Q000378:metabolism*; D005260:Female; D006801:Humans; D008423:Maternal Age; D009865:Oocytes / Q000378:metabolism; D012335:RNA, Ribosomal / Q000096:biosynthesis*
chemical_list: D012335:RNA, Ribosomal