Ask A Scientist Molecular Biology Archive

name         Melanie
status      student
grade        9-12
location     NC

Question -   Where can I find a chromosome map of albinism?
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There are several different genes on several different chromosomes which 
when mutated can cause albinism. The most common gene causing albinism is 
located on chromosome 11. If you search on Google under "albinism gene 
chromosome location" you will find many links.

Ron Baker, Ph.D.
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OMIM, Online Mendelian Inheritance in Man, is an official database of all
genetic disorders known to be caused by a single gene, no matter what the
mode of inheritance of the gene may be. See
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=OMIM.

Search OMIM for albinism and you will find 73 genetic disorders that include
albinism among their symptoms. Almost every chromosome contains a gene or
genes that, when faulty, can cause albinism (all except chromosomes 7, 8,
18, 20, 21, and Y). The commonest types are:

OMIM +203200:
OCULOCUTANEOUS ALBINISM, TYPE II; OCA2, Gene map locus 15q11.2-q12

OMIM #203100:
OCULOCUTANEOUS ALBINISM, TYPE I; OCA1, Gene map locus 11q14-q21

OMIM #606952:
OCULOCUTANEOUS ALBINISM, TYPE IB; OCA1B, Gene map locus 11q14-q21

OMIM +300500:
OCULAR ALBINISM, TYPE I; OA1, Gene map locus Xp22.3

OMIM #203290:
OCULOCUTANEOUS ALBINISM, TYPE III; OCA3, Gene map locus 9p23

Why are there so many albinism genes? Because many steps and processes are
necessary to produce normal pigment. Mistakes can occur at many different
stages of the process.

Here's how to understand the nomenclature for the location (locus) of a gene
on a chromosome:

First the chromosome number is stated, then either p or q. The letter p is
used for the short arm of the chromosome, p for petite in French; q is used
for the long arm of the chromosome. It does not stand for anything but is
used because it follows p. The number(s) that follow are the position on the
chromosome where the gene is found. Under the microscope, chromosomes have a
banded appearance because of the chemicals used in preparing microscope
slides showing chromosomes. Each of the bands is numbered, from 1 near the
centromere to higher numbers further away from the centromere. The gene
OCA1, at locus 11q14-q21, is on the long arm of chromosome 11, somewhere
between band 1, sub-band 4, and band 2, sub-band 1.

Sarina Kopinsky, MSc, CGC
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