Inheritance of Baldness

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Q: Is it true that balding comes from your mother’s father?
A: Possibly. According to studies and reports included in the “Online Mendelian Inheritance in Man” database, maintained and hosted by Johns Hopkins University – a database of genetic research studies and results – there has been evidence that androgenetic alopecia (male pattern baldness) is linked to the X chromosome.
However, the studies which have claimed that male pattern baldness is an autosomal dominant trait – meaning that it only needs one copy of the gene in order to affect the individual – were deemed questionable in validity, and later studies concluded that polygenic inheritance (requiring multiple genetic sourcing and variations) was more likely.
We also know that different environmental and medical factors can greatly affect hair loss, and so it is possible that those individuals who are dealing with baldness are dealing with a culmination of several factors.
As to the specific question of whether balding comes from the mother’s father, you must remember that all we have proof of is the link of hair loss to the X chromosome. Many people presume that because the father determines the femaleness of the individual by the donation of an X chromosome AND that the X chromosome has been linked to hair loss that these two statements form proof that the mother’s father transmits the hair loss tendency.
It’s possible that the hair loss gene could come from the mother’s mother, who also donates an X chromosome to the make-up of a woman’s genetic code. And given the conclusion of the study that multiple gene sourcing was the most likely cause for hair loss, the permutations for concrete genetic cause of hair loss become much more convoluted.
See also:
Hair loss
Testing and treatments for genetic hair loss
Hereditary hair color and how parents determine a baby's hair.