Find out whether your baby is likely to have straight, wavy, curly, or coily hair using TCHH gene inheritance models and incomplete dominance analysis from both parents.
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Generated at traitgen.com, Free genetics education. Not medical advice.
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⚠️ Educational only. Probability estimates based on genetic models, not medical advice.
The tightest hair texture (Type 4 coily) has the highest number of follicles per cm² of any hair type. Despite common misconceptions, coily hair is not fragile by nature , its higher density provides natural protection.
Hair texture is determined by the cross-sectional shape of the hair follicle. Round follicles produce straight hair; oval follicles produce wavy; elliptical follicles produce curly; and highly flattened ribbon-shaped follicles produce coily or kinky hair.
The TCHH gene encodes trichohyalin, a protein in the inner root sheath that influences follicle cross-sectional shape. Specific TCHH variants are strongly associated with the straight-to-wavy hair spectrum in multiple populations.
Hair texture shows incomplete dominance , when parents with different textures have children, the result is often intermediate. Straight and curly parents commonly produce wavy-haired children rather than clearly one or the other, which is why the spectrum is continuous.
EDAR affects follicle density and thickness. WNT10A influences follicle development and structure. Variants across these genes determine the full range of textures globally, from pin-straight to tightly coiled Type 4 hair.
Hair follicle shape can change during puberty due to hormonal influences on follicle geometry. Many children with straight baby hair develop waves or curls by adolescence. Adult texture is usually stable and is the better reference point for genetic prediction.
Not in a simple dominant or recessive sense. Hair texture shows incomplete dominance , when a child inherits alleles associated with different textures, the result is often intermediate rather than purely one or the other. This is why straight and curly parents commonly produce wavy-haired children, and why texture shows a continuous spectrum rather than binary outcomes.
Yes, though uncommon. If both parents carry alleles for tighter curl patterns without fully expressing them , for example, a wavy-haired parent who had a coily-haired grandparent , their child could potentially express a tighter pattern. This is more likely when grandparents have significantly curlier hair than the parents.
Not reliably. Many babies are born with fine, straight hair because follicles are still maturing. As follicle geometry develops during the first years of life, the natural texture often becomes more pronounced. The adult texture is more stable and is the better predictor reference point.
Type 3 curly hair forms defined spiral or ringlet patterns from an oval-shaped follicle. Type 4 coily hair has a much tighter pattern from a highly flattened, ribbon-like follicle. Type 4 is most common in people with sub-Saharan African ancestry and requires different moisture management compared to Type 3 hair.