The area of 1q21.1 is one of the most difficult parts of the human genome to map.Because of the repetitions in 1q21.1, there is a larger chance of an unequal crossing-over during meiosis. CNVs occur due to non-allelic homologous recombination mediated by low copy repeats (sequentially similar regions). Typing
A common deletion is restricted to the distal area. This is a Class I-deletion.In some cases the deletion is so large that the proximal area is involved as well, the so-called Class II-deletion. There are some complex cases in which both the proximal area and the distal area are affected, while the area in between is normal. There are also some a-typical variants. Related genes
Genes related to 1q21.1 deletion in the distal area are PDE4DIP, HYDIN2, PRKAB2, PDIA3P, FMO5, CHD1L, BCL9, ACP6, GJA5, GJA8, NBPF10, GPR89B, GPR89C, PDZK1P1 and NBPF11. Diagnostics
A de novo-situation appears in about 75% of the cases. In 25% of the cases, one of the parents is carrier of the syndrome, without any effect on the parent. Sometimes adults have mild problems with the syndrome. To find out whether either of the parents carries the syndrome, both parents have to be tested. In several cases, the syndrome was identified with the child, because of a developmental disorder or another problem, and later it appeared that the parent was affected as well. In families where both parents have tested negative for the syndrome, chances of a second child with the syndrome are extremely low.
(2004), using Y-chromosomal DNA binary-marker haplotyping, suggested that a cohort of southern Indian hairy-eared males carried Y chromosomes from many haplogroup. The hypothesis of Y- linkage would require multiple independent mutations within a single population. No significant difference between the Y-haplogroup frequencies of hairy-eared males and those of a geographically matched control sample of unaffected males was established. The study concluded that auricular hypertrichosis is not Y-linked in southern India, though this result may not apply to all to all populations. See also
Ear hair
Hypertrichosis


== References ==