My Indicators for Left-handedness and Ambidexterity Based on GWAS study that identifies 48 common genetic variants associated with handedness.

I was reading a 2020 Genome-wide association study that identifies 48 common genetic variants associated with handedness.

Abstract

Handedness has been extensively studied because of its relationship with language and the over-representation of left-handers in some neurodevelopmental disorders. Using data from the UK Biobank, 23andMe and the International Handedness Consortium, we conducted a genome-wide association meta-analysis of handedness (N = 1,766,671). We found 41 loci associated (P < 5 × 10–8) with left-handedness and 7 associated with ambidexterity. Tissue-enrichment analysis implicated the CNS in the aetiology of handedness. Pathways including regulation of microtubules and brain morphology were also highlighted. We found suggestive positive genetic correlations between left-handedness and neuropsychiatric traits, including schizophrenia and bipolar disorder. Furthermore, the genetic correlation between left-handedness and ambidexterity is low (r G = 0.26), which implies that these traits are largely influenced by different genetic mechanisms. Our findings suggest that handedness is highly polygenic and that the genetic variants that predispose to left-handedness may underlie part of the association with some psychiatric disorders.

Handedness refers to the preferential use of one hand over the other. Conversely, ambidexterity refers to the ability to perform the same action equally well with both hands. Hand preference is first observed during gestation as embryos begin to exhibit single arm movements1,2. Across the life span, the consistent use of one hand leads to alterations in the macromorphology and micromorphology of bone3, which results in enduring asymmetries in bone form and density4,5. At the neurological level, handedness is associated with the lateralization of language (the side of the brain involved in language) and other cognitive effects6,7. The prevalence of left-handedness in modern western cultures is approximately 9%8 and is greater in males than females9. While handedness is conceptually simple, its aetiology and whether it is related to brain and visceral (internal organ) asymmetry is unclear.

Since the mid-1980s, the literature regarding the genetics of handedness and lateralization has been dominated by the right-shift10 and dextral-chance11 theories. Both theories involve additive biallelic monogenic systems in which an allele at the locus biases an individual towards right-handedness, while the second allele is a null allele that results in the random determination of handedness by fluctuating asymmetry. The allele frequency of the right-shift variant has been estimated at ~43.5%10, while that of the dextral-chance variant has been estimated at ~20% in populations with a 10% prevalence of left-handedness11. A joint analysis of data from 35 twin studies found that additive genetic factors accounted for 25.5% (95% confidence interval (CI) of 15.7, 29.5%) of the phenotypic variance of handedness12, which is consistent with predictions of the variance explained under the single gene right-shift and dextral-change models. However, linkage studies13–16, candidate gene and genome-wide association studies (GWAS)17–21 have failed to identify any putative major gene for handedness.

Most recently, two large-scale GWAS identified four genomic loci containing common variants of small effect associated with handedness20,21. However, both GWAS failed to replicate signals at the LRRTM1, PCSK6 and the X-linked androgen receptor genes that had previously been reported in smaller genetic association studies17–19. In this study, we present findings from the world’s largest GWAS meta-analysis of handedness to date (N = 1,766,671), which combined data from 32 cohorts from the International Handedness Consortium (IHC) (N = 125,612), 23andMe (N = 1,178,877) and the UK Biobank (UKBB) (N = 462,182).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7116623/

I looked at my own in Sequencing.com's Genome Explorer. I also checked my mother's.

I have 19 of the 41 Lefthandedness Variants, and two of them are homozygous which means that I have two copies of the effect allele.

I have 1 of the 7 Ambidexterity Variants.

I am righthanded, but I am a left-eye dominant.

I am a neurodivergent with Dyslexia, Dyspraxia, ADHD.

With the coordination problems of Dyspraxia, I had problems with gross and fine motor skills.

Because of my problems with speech, coordination, and balance, I was examined by neurologist in early childhood but no brain damage was found.

I had therapy to help me with my fine motor skills.

I was late establishing a dominant hand. My mother told me that she thought I was going to be ambidexterous. One of my aunts told me that she and the other relatives were uncertain about which I hand that I should be holding things with when they would give me things to hold when I was little.

My maternal grandfather was left-handed, and one of my maternal uncles is lefthanded.

When I was a student in special education class in early childhood, the teachers would attempt to correct the way I wrote with my right hand. It was to no avail. I always wrote the same way as I did as a little kid.

Over the years, people told me that I write like a left-handed person.

As I get older and not writing much, I have noticed difficulty with my handwriting.

I tend to struggle. It's like my hand and brain are fighting each other when I am writing.

The table with list of variants

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7116623/table/T1/?report=objectonly

LEFTHANDEDNESS VARIANTS

rs4953572 G/A FOXN2 Mom has it too