Unbalanced/balanced chromosomal rearrangements

Question

A) If someone is heterozygous for chromosomal duplication, will the rearrangement be balanced or unbalanced in a somatic cell? How about a gamete? How does this change if the individual is homozygous for the duplication?

A) If someone is heterozygous for a reciprocal translocation, will the rearrangement be balanced or unbalanced in a somatic cell? How about a gamete? How does this change if the individual is homozygous for the translocation?

Answer 1

A chromosomal duplication, by definition, creates extra genetic information. That should be enough to tell you that any cell with a chromosomal duplication, somatic or gamete, homozygous or heterozygous, will be unbalanced in its arrangement.

A reciprocal chromosomal translocation, on the other hand, does not add or remove any material. As such, homozygous somatic cells will be balanced in their arrangements. A heterozygous somatic cell would be unbalanced, as the rearrangement of material on one copy of the DNA would not be mirrored in the other copy. Thinking carefully about the process of meiosis, one would realize that the separation of genetic material into haploid cells will result in gametes which are unbalanced.