Question

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?

The chromosome number in trisomy would be normal; in a duplication, there would be one more chromosome.

In both cases there would be an extra chromosome, but in trisomy there would be three chromatids on one chromosome and in a duplication there would be two chromatids on one chromosome.

In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.

The chromosome number in both cases would be normal, but in trisomy there would be three chromatids on one chromosome and in a duplication there would be two chromatids on one chromosome.

Answer 1

The correct answer is: In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.

Trisomy is a type of polysomy (chromosome aberration with extra number of chromosome/s) and also type of aneuploidy (an abnormal number of chromosomes).

Instead of the normal two (one from mother one from father) chromosomes, people with trisomy have three chromosomes. This condition occurs when chromosome pairs fail to separate properly during cell division.

Duplication, on the other hand, usually refers to a region of DNA that is being duplicated. This condition occurs as products of several types of errors in DNA replication and repair machinery.