Causes Chromosome 4, Monosomy 4q is caused by a partial deletion of the long arm of chromosome 4.
[rarediseases.org]
[…] q long arm of chromosome r ring chromosome 46,X,r(X) Female with ring X chromosome rcp reciprocal translocation rob Robertsonian translocation t translocation 46,XX,t(2;8
[radford.edu]
For example, “18q21” refers to band 21 of the long arm of chromosome 18.
[rarediseases.org]