Answer from: Maria José Mendiola, MD, MSc in Human Genetics, MSc in Science Communication, ObGyn
Chromosomal disorders can result from changes in the number or structure or in the number or either the structure of the chromosomes. What does it mean – we have chromosome disorders that can be classified into two main types: first we have the numerical disorders that occur when there is a change in the number of chromosomes. The normal number is 46 chromosomes so in this case, we have more or fewer than 46. Examples of numerical disorders include trisomy, monosomy. Probably one of the most well-known numerical disorders is Down syndrome of trisomy 21. We have other common types of numerical disorders that include trisomy 13, 19 Turner syndrome. Other structural chromosomal disorders result from breakages within chromosomes. They break so, in these types of disorders there may be more or less than two copies of any gene – there is a difference in the number of copies of genes that may lead to clinical differences in affected individuals, for example, we could have chromosome modulations, duplications, balance translocations and balanced translocations or inversions that can affect all the individuals that could have these structural chromosome disorders.
