Crossing over is essential for the normal segregation of chromosomes during meiosis. Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical.
I just found this on google
The piano could only be played with 12 fingers, which is rare because humans normally have ten fingers.
Because they take up both parts of traits so that makes it group to similar organisms
