What would be accomplished if crossing over occurred between sister chromatids? explain

Since sister chromatids are identical, genetic variation will not be produced in the daughter cells.

Explanation:

Sister Chromatid Exchange (SCE):

This is a rare recombination phenomena that entails recombination and crossing over between two sister chromatids. This is contrary to normal recombination in which crossing over between non-sister chromatids takes place, producing genetically variable daughter cells. Exchange of genes between sister chromatids does not produce genetic variations. SCE is actually an indicator of chromosomal instability and DNA repair and replication malfunction. SCE is observed to be increased in pathological conditions like Bloom syndrome (genetic disorder) and Behcet disease (chronic inflammatory disorder) etc.