Editing Sexual orientation (section)

==== Genetic factors ====

[[Gene]]s may be related to the development of sexual orientation. A twin study from 2001 appears to exclude genes as a major factor,<ref name="twin-adol" /> while a twin study from 2010 found that homosexuality was explained by both genes and environmental factors.<ref>{{Cite journal|last1=Långström|first1=Niklas|last2=Rahman|first2=Qazi|last3=Carlström|first3=Eva|last4=Lichtenstein|first4=Paul|date=2010-02-01|title=Genetic and Environmental Effects on Same-sex Sexual Behavior: A Population Study of Twins in Sweden|journal=Archives of Sexual Behavior|language=en|volume=39|issue=1|pages=75–80|doi=10.1007/s10508-008-9386-1|issn=0004-0002|pmid=18536986|s2cid=11870487}}</ref> However, [[experimental design]] of the available twin studies has made their interpretation difficult.

In 2012, a large, comprehensive&nbsp;[[Genome-wide association study|genome-wide linkage study]]&nbsp;of male sexual orientation was conducted by several independent groups of researchers. Significant linkage to homosexuality was found with genes on chromosome [[Xq28]] and chromosome 8 in the pericentromeric region. The authors concluded that "our findings, taken in context with previous work, suggest that genetic variation in each of these regions contributes to development of the important psychological trait of male sexual orientation." It was the largest study of the genetic basis of homosexuality to date and was published online in November 2014.<ref>{{cite journal|last1=Sanders|first1=A.R.|last2=Martin|first2=E.R.|last3=Beecham|first3=G.W.|last4=Guo|first4=S.|last5=Dawood|first5=K.|last6=Rieger|first6=G.|last7=Badner|first7=J.A.|last8=Gershon|first8=E.S.|last9=Krishnappa|first9=R.S.|last10=Kolundzija|first10=A.B.|last11=Duan|first11=J.|last12=Gejman|first12=P.V.|last13=Bailey|first13=J. M.|title=Genome-wide scan demonstrates significant linkage for male sexual orientation|journal=Psychological Medicine|date=17 November 2014|volume=45|issue=7|pages=1379–1388|doi=10.1017/S0033291714002451|pmid=25399360|s2cid=4027333 |s2cid-access=free |url=http://biology-web.nmsu.edu/~houde/Sanders%20et%20al%202014.pdf |url-status=dead |archive-url=https://web.archive.org/web/20171031013213/http://biology-web.nmsu.edu/~houde/Sanders%20et%20al%202014.pdf |archive-date= Oct 31, 2017}}</ref>

However, in August 2019, a [[genome-wide association study]] of 493,001 individuals concluded that hundreds or thousands of genetic variants underlie homosexual behavior in both sexes, with 5 variants in particular being significantly associated. They stated that in contrast to linkage studies that found substantial association of sexual orientation with variants on the X-chromosome, they found no excess of signal (and no individual genome-wide significant variants) on Xq28 or the rest of the X chromosome.<ref>
*{{cite journal |last1=Zietsch |first1=Brendan P. |last2=Neale |first2=Benjamin M. |last3=Perry |first3=John R. B. |last4=Sanders |first4=Alan R. |last5=Martin |first5=Eden R. |last6=Beecham |first6=Gary W. |last7=Harris |first7=Kathleen Mullan |last8=Auton |first8=Adam |last9=Långström |first9=Niklas |last10=Lundström |first10=Sebastian |last11=Lichtenstein |first11=Paul |last12=((23andMe Research Team)) |last13=Sathirapongsasuti |first13=J. Fah |last14=Guo |first14=Shengru |last15=Abdellaoui |first15=Abdel |last16=Busch |first16=Alexander S. |last17=Wedow |first17=Robbee |last18=Maier |first18=Robert |last19=Nivard |first19=Michel G. |last20=Verweij |first20=Karin J. H. |last21=Ganna |first21=Andrea |title=Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior |journal=Science |date=30 August 2019 |volume=365 |issue=6456 |pages=eaat7693 |doi=10.1126/science.aat7693 |pmid=31467194 |language=en |issn=0036-8075|pmc=7082777 |doi-access=free }}
*{{cite web |title=Genetics of Sexual Behavior |url=https://geneticsexbehavior.info/what-we-found/ |website=Genetics of Sexual Behavior |publisher=geneticsexbehavior.info |access-date=30 August 2019 |date=28 February 2018}}
*{{cite journal |last1=Lambert |first1=Jonathan |title=No 'gay gene': Massive study homes in on genetic basis of human sexuality |journal=Nature |volume=573 |issue=7772 |pages=14–15 |date=29 August 2019 |doi=10.1038/d41586-019-02585-6 |pmid=31481774 |language=en|bibcode=2019Natur.573...14L |doi-access=free }}</ref>