For a Eukaryotic animal cell, is it generally more deleterious to be triploid or to have trisomy of a single chromosome?

Question

For a Eukaryotic animal cell, is it generally more deleterious to be triploid or to have trisomy of a single chromosome? Why is triploidy an impossible long-term state for the generations to come after a triploid organism that reproduces sexually?

Answer 1

Hi Alizee! It is generally more deleterious to be triploid.

Having just a single extra chromosome is an abnormality and often leads to many issues and disorders. For example think of Down Syndrome (Trisomy 21). The common symptoms are mental impairment and stunted growth just to list a few. Now imagine that every chromosome had an extra copy. It would be expected that the symptoms would be much more severe. Triploidy leads to infant death usually within a few days of delivery, while to contrast that there are many trisomy individuals that live into adulthood.

To answer your second question, triploid organisms are usually sterile. They lack homologous chromosomes which leads to the prevention of pairing during meiosis. Since there is a set of extra chromosomes, you would assume that they would not line up the same way during meiosis and would not divide into their correct haploid cells.

Let me know if this makes sense, or if you would like any more clarification!