What is a 22q11 deletion?
In humans, DNA, which encodes the master plan for our bodies, is organized as 23 pairs of chromosomes. One pair, the sex chromosomes, consists of either two X chromosomes (XX), resulting in a girl, or one X and one Y chromosome (XY), resulting in a boy. The other 22 pairs of chromosomes, referred to as the autosomes, are numbered 1 through 22. While some of the DNA code can vary between individuals, the overall appearance of each chromosome is unique when viewed under a microscope with staining. Each chromosome is organized into two or three parts: a short arm (not present for some chromosomes), a central portion called the centromere, and a long arm. The arms contain the DNA sequences that encode the genes. The long arm is called by the number of the autosome and “q”. Therefore, the long arm of chromosome 22 is called 22q. Chromosomal arms also have sections that appear as light or dark bands after special staining, which are numbered. Thus, 22q11 refers to the 11 band (pronounced one
