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{{Redirect|GCTA|the TV camera used in the Apollo space program|Apollo TV camera#RCA J-Series Ground-Commanded Television Assembly (GCTA){{!}}Apollo TV camera}}
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{{technical|date=January 2017}}
'''Genome-wide complex trait analysis (GCTA) Genome-based [[restricted maximum likelihood]] (GREML)''' is a statistical method for [[variance]] component estimation in genetics which quantifies the total narrow-sense (additive) contribution to a trait's [[heritability]] of a particular subset of genetic variants (typically limited to [[Single-nucleotide polymorphism|SNPs]] with [[Minor allele frequency|MAF]] >1%, hence terms such as "chip heritability"/"SNP heritability"). This is done by directly quantifying the chance genetic similarity of unrelated strangers and comparing it to their measured similarity on a trait; if two strangers are relatively similar genetically and also have similar trait measurements, then this indicates that the measured genetics causally influence that trait, and how much. This can be seen as plotting prediction error against relatedness.<ref>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3232052/figure/F3/ Figure 3] of Yang et al 2010, or Figure 3 of Ritland & Ritland 1996</ref> The GCTA framework extends to bivariate [[genetic correlation]]s between traits;<ref name="Lee2012">Lee et al 2012, [http://bioinformatics.oxfordjournals.org/content/28/19/2540.full "Estimation of pleiotropy between complex diseases using single-nucleotide polymorphism-derived genomic relationships and restricted maximum likelihood"]</ref> it can also be done on a per-[[chromosome]] basis comparing against chromosome length; and it can also examine changes in heritability over aging and development.<ref name="Deary2012"/> There is an ongoing debate about whether GCTA generates reliable or stable estimates of heritability when used on current SNP data.<ref>{{Cite journal |last=Krishna Kumar |first=Siddharth |last2=Feldman |first2=Marcus W. |last3=Rehkopf |first3=David H. |last4=Tuljapurkar |first4=Shripad |date=2016-01-05 |title=Limitations of GCTA as a solution to the missing heritability problem |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=113 |issue=1 |pages=E61–70 |doi=10.1073/pnas.1520109113 |issn=1091-6490 |pmc=4711841 |pmid=26699465}}</ref>
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