核仁小而常为圆形的颗粒体，由蛋白质和细胞核中的核糖核酸构成，通常与一特定染色体缔合有直接关系并涉及核糖体核糖核酸的合成和核糖体的形成

• A small, typically round, granular body composed of protein and RNA in the nucleus of a cell, usually associated with a specific chromosomal site and involved in ribosomal RNA synthesis and the formation of ribosomes.