The most likely effect of FGF5 mutation is an increase on the ratio of hairs in the growth phase to hairs in rest phase compared with the ratio when the normal FGF5 allele. It leads to trichomegaly.
The FGF5 gene code for glycosaminoglycan binding proteins, which are commonly expressed in the root sheath of the hair follicle.
The maximum FGF5 gene expression occurs in the late anagen step (i.e., when the hair follicle forms a new hair shaft) of the hair cycle.
Mutations of this gene (FGF5) produce trichomegaly, thereby increasing the portion of hair in the anagen phase.
Learn more about the anagen phase here:
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