How to calculate chromosome pairing in descending order in idiogram?
Answers
Answer: As a mechanism for facilitating data presentation and for comparing results obtained by different investigators, the light and dark bands observed in a raw karyotype are usually converted into idiograms, which are black and white drawings of idealized chromosomes as shown in Autosomes are numbered from 1 to 19, in descending order of length. Major bands (alternating dark and light regions) within each autosome are designated with a capital letter starting from A at the centromere, and ascending in alphabetical order. With an increase in resolution, most major bands can be resolved into a series of smaller bands, which are numbered sequentially from 1 starting at the proximal — or centromeric — side of the major band and ending at the distal — or telomeric — side. Finally, when increased resolution allows the visualization of multiple minor bands within a single previously defined sub-band, these are designated with a number (in sequence from 1) demarcated with a decimal point. As an example of the use of this nomenclature, the designation 17E1.3 represents (in reverse order), the third minor band within the first sub-band within the fifth major band (all in order from the centromere) on the mouse chromosome ranked seventeenth in size.