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Name: Amber A.
Status: Student
Age: 15
Location: N/A
Country: N/A
Date: March 2004


Question:
What are the possible genotypes and phenotypes for baldness? What is the chromosome number for the gene for baldness as well as the gene's location on the chromosome?



Replies:
Answer: Many types of baldness occur, and often baldness may be a symptom of some other illness or genetic condition or syndrome. The most common type of baldness in healthy men has also been called "early baldness of the ordinary type" or "male patterned baldness (MPB)" or androgenetic alopecia.

Some studies have concluded that this type of baldness is caused by an autosomal gene situated somewhere on chromosomes 1 through 22, not on the X or Y chromosomes. The exact chromosomal location has not yet been identified - we don't know which chromosome, or which position on that chromosome.

The gene appears to be autosomal dominant in males and autosomal recessive in females. This means that some other gene or genes must be influencing the way the gene is expressed.

Males who have just one copy of the gene will, of course, also have one copy of the corresponding non-baldness gene, since all our genes occur in pairs. In other words, these males are heterozygous for the gene. Such heterozygous males do have baldness, according to this theory.

A female who is heterozygous, with one baldness gene and one non-baldness gene, will not be bald. She can still pass the gene onto her sons and daughters, but a woman will not be bald herself unless she inherits a baldness gene from both parents. In such a case she would be homozygous for the baldness gene.

You may wonder how it is that we do not know where this gene is on the chromosomes, now that the Human Genome Project has been completed. The answer is that the Human Genome Project gives us only the sequence of DNA base pairs along the length of the chromosomes - ACGTACGT, etc. The next challenge is to interpret these sequences and figure out which gene is which. DNA-language is not so easy to understand even when we can read the sequence.

Please note that there are also other studies of baldness that seem to indicate other modes of inheritance different from the inheritance pattern described above. Perhaps we may still identify other genes that cause baldness in certain families.

In general, it is probably easier for scientists to secure funding for research into serious medical conditions than for research into cosmetic situations like baldness that do not have a huge impact on people's health.

Sarina Kopinsky, MSc, H.Dip.Ed.



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