1134
Given the dominant role of p21 in p53 cell cycle control , we crossed Trp53 ( 515C / 515C ) mice onto a p21 - null background to determine whether p21 was required for maintaining chromosomal stability and delaying tumor onset .
 Anatomy: cell; Anatomy: chromosomal; Anatomy: tumor
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Anatomy 
Text: {0} 
Answer:
 Anatomy: cell; Anatomy: chromosomal; Anatomy: tumor