Cytogenetics is a branch of genetics that is concerned with the study of the structure and function of the cell, especially the chromosomes.  Rice cytogenetics is used to identify differences in the DNA or chromosomes by examining the chromosomes found in the root tips (mitotic cells) of rice plants or the chromosome pairing found in immature pollen (meiotic cells).  Analysis of the chromosome pairing found in hybrid plants obtained by crossing cultivated rice and ancestral rice can be used to determine the relationship between the two species.