GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2010-03 > 1268433478
From: "RICHARD KENYON" <>
Subject: Re: [DNA] Occular Albanism
Date: Fri, 12 Mar 2010 14:37:58 -0800
Perhaps the following from "A Dictionary of Genetics", 7th Ed., by King, Stansfield, and Mulligan, Oxford Press, 2006, will help
Albinism. 1. deficiency of chromoplasts in plants. 2. the inability to form melanin in the eyes, skin, and hair, due to a tyrosinase deficiency. In humans the condition is inherited as an autosomal recessive. Tyrosinase (TYR) is an essential enzyme for melanin synthesis, and some mutations in the tyrosinase gene (tyr) results in oculocutaneous albinism (OCA). The TYR gene is located in 11q14-21; it contains five exons, and its mRNA is 2,384 nucleotides long. More than 90 mutations have been identified, most of the missense type. One such mutation in codon 422 results in the substitution of glutamine for arginine. The changed enzyme is heat-sensitive and so mimics the temperature-sensitive enzymes known as the Himalayan strains of mice, rabbits, and other species.
So quite a bit is known about albinism in humans, mainly that mutations on chromosome 11 are responsible and that it is an autosomal recessive trait. Thus both parents need to have the mutation for albinism to appear. If only one parent had the mutation, the person would not be an albino, but they would be a carrier of albinism.
I was going to say that it isn't X-linked recessive, but then I looked up "Ocular Albinism" in the same dictionary where it states:
ocular albinism. a hereditary eye disease of humans that occurs in two forms, one inherited as an autosomal recessive and the other X-linked. The X-linked condition is the most common form of ocular albinism. In males, the prevalence of the disease is 1/50,000. The normal gene is at Xp22.3, and it encodes a protein that contains 424 amino acids. This is located in the membranes of melanosomes but is not a tyrosinase. Males show a reduced pigmentation of the retina and iris but not of the hair or skin. They are extremely sensitive to light and have reduced visual acuity. Patients with ocular albinism or oculocutaneous albinism have a misrouting of the optic tracts, which results in a loss of stereoscopic vision. In heterozygous females, retinas show a mosaic pattern of pigment distribution due to random inactivation of the X chromosomes during the early development of the eye.
Some of this jargon may be unfamiliar to many, but this may help. While they state that the more common X-linked ocular abinism is located within Xp22.3 they do not specify the name of the gene or its exact location. I would think your mother could have gotten the mutation from either of her parents. I suppose if a female had the mutation in both of her X-chromosomes, she would exhibit ocular albinism. But I assume the odds of this would be 1 in 50,000 squared, or 1 in 2.5 billion. So there's good reason it has probably not been observed.
Richard R. Kenyon ("Dick")
----- Original Message -----
From: Ron Long<mailto:>
Sent: Friday, March 12, 2010 1:17 PM
Subject: [DNA] Occular Albanism
I have what I think is an unusual idea for genetic research.
Occular Albanism is an X-linked recessive, so a male with it (me) got it from his mother, and she got it from her father, and the father got it from the grandmother who got it from her father etc. Women usually don't exhibit the symptoms at lest as much.
Okay so I don't have any idea who my great-grandmother's father was. She was born abut 1870 in Western Arkansas. So I'm thinking that there are probably some other people who also have the condition today who are descendants of the same fellow. I'd like to start or join a group of persons with occular albanism who share their genealogies in order to trace the condition back to common ancestors.
Is there such a group? How could such a group be started? Anyone have any ideas?