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== Genetics == | == Genetics == | ||
=== ''ALDH2'' === | === ''ALDH2'' === | ||
''ALDH2'' is a ~43 kb gene on chromosome 12 consisting of 13 exons and encodes the ALDH2 enzyme found in the mitochondria, it has two alleles ''ALDH2*1'' and ''ALDH2*2''. The [http://www.ncbi.nlm.nih.gov/SNP/snp_ref.cgi?rs=rs671 rs671 SNP] ([ | ''ALDH2'' is a ~43 kb gene on chromosome 12 consisting of 13 exons and encodes the ALDH2 enzyme found in the mitochondria, it has two alleles ''ALDH2*1'' and ''ALDH2*2''. The [http://www.ncbi.nlm.nih.gov/SNP/snp_ref.cgi?rs=rs671 rs671 SNP] ([http://wiki.london.hackspace.org.uk/view/Project:Alcohol_Flush_Genotyping#rs671_FASTA_sequence FASTA]), in which a guanine in the ancestral ''ALDH2*1'' is substituted for an adenine in ''ALDH2*2'' is responsible for these two alleles. The G -> A substitution in ''ALDH2*2'' causes the amino acid lysine to be expressed instead of glutamate and causes an inactive ALDH2 enzyme to be expressed. ''ALDH2*2'' is considered nearly dominant as heterozygous individuals have almost no detectable ALDH2 activity in the liver and people who carry two copies of the ''ALDH2*2' allele have no detectable activity. | ||
The inactivity of the ALDH2 enzyme in individuals with at least one ''ALDH2*2'' allele causes acetaldehyde levels in the blood to increase after the imbibing of alcohol to a level high enough to cause a flushing reaction and possibly nausea or increased heart rate. | The inactivity of the ALDH2 enzyme in individuals with at least one ''ALDH2*2'' allele causes acetaldehyde levels in the blood to increase after the imbibing of alcohol to a level high enough to cause a flushing reaction and possibly nausea or increased heart rate. |