(c) : Centromere is the point at which the two chromatids of a chromosome are held together. During movement of chromosomes, the spindle fibres (on which the chromatids move) are attached to the centromere. Crossing over involves physical exchange of genetic material between non-sister chromatids of homologous chromosomes. Cytoplasmic cleavage is the division of cytoplasm. Transcription is the process in which the genetic information of DNA is transferred to m RNA as the first step in protein synthesis.