Variations in a region of the short (p) arm of chromosome 5 designated 5p13.1 are also associated with Crohn disease risk.

Black midget with cri du chat-90Black midget with cri du chat-85

Together, these variations are known as the inflammatory bowel disease 5 (IBD5) locus.

This region of chromosome 5 contains several related genes that may influence Crohn disease risk, including .

Humans normally have 46 chromosomes in each cell, divided into 23 pairs.

Two copies of chromosome 5, one copy inherited from each parent, form one of the pairs.

This deletion occurs in immature blood cells during a person's lifetime and affects one copy of chromosome 5 in each cell.

5q- syndrome is a type of bone marrow disorder called myelodysplastic syndrome (MDS), in which immature blood cells fail to develop normally.

Researchers have also defined regions of the short arm of chromosome 5 that are associated with particular features of cri-du-chat syndrome.

A specific region designated 5p15.3 is associated with a cat-like cry, and a nearby region called 5p15.2 is associated with intellectual disability, small head size (microcephaly), and distinctive facial features.

Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies.