Evidence · Replicated

What the research found

In the cited research, the T allele at rs11803731 was associated with straighter scalp hair.

AA: Curlier
AT: Middle
TT: Straighter

Modest effect

What the study found

In the study, each copy went with lower hair curl on the study's underlying straight to curly scale on average.

Australian adolescent twins and their siblings of European descent · 1,649 people · Table 3 (adolescent sample) and its footnote aCommon variants in the trichohyalin gene are associated with straight hair in Europeans (Medland et al., 2009)

Evidence: Replicated genome-wide association
Who was studied: European and admixed Latin American cohorts

1000 Genomes Project

How common each genotype is

How common each genotype is in the 1000 Genomes Project, by region
Region	AACurlier	ATMiddle	TTStraighter
All regions2,504 people	87%	12%	1%
Africa661 people	>99%	<1%	Not seen
The Americas347 people	82%	17%	<1%
East Asia504 people	>99%	<1%	Not seen
Europe503 people	60%	33%	6%
South Asia489 people	88%	12%	<1%

Among the 2,504 people of the 1000 Genomes Project, in five world regions. These percentages describe groups of people, never anyone’s chance of having a trait.

Ancient genomes

Through time

How often the studied letter was read in ancient people, era by era, in the region chosen.

Region

Through time: Europe
Before farmingbefore 6500 BC	32%24 of 75 copies read
First farmers6500 to 3000 BC	42%317 of 758 copies read
Bronze Age3000 to 1200 BC	36%241 of 670 copies read
Iron Age and Antiquity1200 BC to AD 600	30%360 of 1,218 copies read
Middle AgesAD 600 to 1500	26%250 of 978 copies read
Today1000 Genomes	23%230 of 1,006 copies

Neanderthal and Denisovan genomes

Altai Neanderthal: No copies
Vindija Neanderthal: No copies
Chagyrskaya Neanderthal: No copies
Denisovan: No copies

Neanderthals and Denisovans carried the other letter, so this letter is younger than our split with them.

For most ancient people only one of their two copies can be read, so these counts are copies read, not people. Close relatives, repeated samples and samples the archive marks as unreliable are left out. Ancient genomes from the Allen Ancient DNA Resource (AADR v66): 15,136 people.

rs11803731

The marker

Gene or region: TCHH
Marker: rs11803731
Location: Chromosome 1 · GRCh37 152,083,325 · GRCh38 152,110,849
Letters studied: A and T, with T as the studied allele

A DNA Traits report reads this marker in your raw DNA file and shows which of the three genotypes is yours, with how common it is. It counts the copies of the studied allele; it does not measure the trait itself.

Marker: TCHH · rs11803731
Location: Chromosome 1 · GRCh37 152,083,325 · GRCh38 152,110,849
Studied allele: T
Published statistic: Liability-threshold beta per T allele (toward straight): 0.42 in adolescents (n 1649, P 1.76e-11), 0.50 in adults S1 (n 1945, P 2.51e-12), 0.44 in adults S2 (n 1251, P 1.37e-10); meta-analysis P 3.18e-31; 6.11% of variance (Medland 2009 Table 3). CANDELA replication P 3e-12 (Adhikari 2016 Table 1); 0.42 SD per copy (Table 3 (adolescent sample) and its footnote a)
1000 Genomes Project phase 3, people with 0, 1 and 2 copies: All regions 2176 / 292 / 36 · Africa 655 / 6 / 0 · The Americas 285 / 59 / 3 · East Asia 503 / 1 / 0 · Europe 304 / 168 / 31 · South Asia 429 / 58 / 2

See this card in the sample report

Limits

What it cannot tell you

Hair shape depends on many genes. This TCHH association is not a curl classification or a prediction of texture.

A genome-wide association scan in admixed Latin Americans identifies loci influencing facial and scalp hair features (Adhikari et al., 2016)

The same topic

More in Appearance

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