Answer: Four, two
Explanation:
FISH (fluorescence in situ hybridization) is a technique for chromosome mapping with probes that emit fluorescence and allow the visualization, distinction and study of chromosomes of nuclei in metaphase or inferophase. In this way, any type of anomaly such as inversions, aneuploidies, duplications or microdeletions can be seen. To do this, a non-specific DNA staining is performed with DAPI (a fluorophore that marks the nucleus where DNA is present) and the fluorescence will be seen under the microscope.
When cells are in metaphase, their chromosomes are condensed in preparation for cell division. To stop them in metaphase, colchicine is used which is a microtubule depolymerizing agent responsible for separating the sister chromatids of a chromosome, thus preventing the progression of cell division and arresting the cell cycle in metaphase. Here we will see translocations, microdeletions or duplications.
Interphase FISH is used to see decondensed chromatin, which allows higher resolution in detecting small abnormalities. It is mainly used for the detection of aneuploidies or large deletions, duplications or translocations when samples are difficult to grow or are scarce, as in the case of fetal or tumor cells. It is not possible to distinguish between a normal karyotype and a karyotype showing a balanced translocation. In addition, it can be used in the analysis of solid tumors, which divide very infrequently.
During metaphase, the chromosomes are duplicated so there would be two sets of chromosomes (a total of four chromosomes). Then, there would be four signals for each probe. During interphase, the chromosomes are not dupicated. Since it is a diploid organisms, there would be two chromosomes and this will represen two signals for probe.
