There is no such thing as a "trichomosome". It seems like you might be thinking of a trisomy, which refers to a condition where there are three copies of a particular chromosome instead of the usual two.

For example, Down syndrome is caused by trisomy 21, meaning there are three copies of chromosome 21.

If you're interested in learning more about trisomy or other chromosomal abnormalities, I recommend checking out resources from reputable organizations like the National Human Genome Research Institute (NHGRI) or the Genetic and Rare Diseases Information Center (GARD).