What is the principle behind the Microsort technique?

The Microsort technique is based on the differential staining of spermatozoa that carry either X or Y chromosomes. The principle relies on the fact that the X chromosome absorbs more dye than the Y chromosome, due to intrinsic differences in their structure, most notably the size and genetic material they contain. This differential absorption allows the X chromosome to take on a positive charge when stained.

When sperm are stained, the X chromosome-bearing sperm are heavier because they contain more genetic material than the Y chromosome-bearing sperm. The positive charge allows for sorting using a flow cytometry method, where the sperm can be categorized based on their charge and subsequently selected for artificial insemination or IVF procedures. This allows for a biased selection of the desired sex, which is the primary purpose of using the Microsort technique.

Other choices incorrectly represent the properties of the chromosomes or their behavior during the sorting process. For instance, dye absorption isn't a matter of weight, but rather of the chemical properties specific to the chromosomes.