You are studying mitosis in cultured cells. These are transformed (cancerous) an

Question

You are studying mitosis in cultured cells. These are transformed (cancerous) and as a result bypass the metaphase/anaphase checkpoint. You have one cell line that has a loss of function mutation in separase and another strain that has a loss of function mutation in cohesion. Both cell lines are more prone to non-disjunction than other transfomed cell lines despite the fact that cohesion and separase have opposite functions: cohesion holds sister chromatids together while separase allows sister chromatids to separe. Explain why the cells wiht a cohesion mutation display non disjunction. Explain why the cells with a separase mutation display non-disjunction.

Explanation / Answer

Both mitosis and meiosis require cohesion to keep the sister chromatids together until separation is imminent at anaphase. Cohesion is established during DNA replication before both mitosis and meiosis by multiprotein subunit complexes called cohesins.

The reason behind coherase exhibiting non diskunction inspite of its function being keeping the chromatids close together may be the mutation in the functional region of the gene i.e exon which has impaired its function. Similarly separase also suffers mutation but probably in ts intron region that is why its function is not lost and it displays non disjunction.

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