“Human Chromosome Trisomy (Down and Sex-Y)”, was the topic of an earlier blog post. That blog post displayed the chromosomes 21 and Y (shown atop here). The two chromosomes are 50 million base pairs (Y-chromosome), and 46 million base pairs (21-chromosome) in DNA length long. At bottom of the chart below is Y-chromosome and 21-chromosome are in group “G”. The Y=50=DAZ + LWD + RBMY1A1 + USP9Y. The abbreviations communicate the same thing as the words compactly. 21-chromosome equates to the sum of 17 symbols below: ANKRD21 + APP + CBS … etcetera… TFF3 = 46 million base pairs = 21-chromosome. A cytogenetics technician has these terms memorized.