The Adh2 gene of maize has a nucleotide sequence closely related to that of the maize Adh1 gene indicating that the two genes arose from a progenitor gene by a duplication event. The coding regions are 82% conserved at the nucleotide level and 87% conserved at the amino acid level. Each gene has nine introns in identical positions but their nucleotide sequences and lengths differ. Adh2 encodes a single mRNA and has a possible polyadenylation signal, AATAAT, fifteen bases upstream from the polyadenylation site. The Adh2 gene together with the Adh1 gene is induced by anaerobic conditions and under these conditions produces an increased level of mRNA. The 5′ untranslated regions of the transcripts of Adh1 (100 bp) and Adh2 (126 bp) have diverged in sequence except for a conserved region which may be important for their anaerobic-specific translation. The 3′ and 5′ flanking sequences of the two genes are also divergent except for 11 bp of precise homology around the TATA boxes and three other 8 bp sequences further upstream. One of the common 8 bp sequences (CACCTCCC) is in a similar position (-150 bp to -200 bp) in the two genes and may have a regulatory function in gene expression.
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