id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-274375-a11ztdpg	Zhang, Yiqiang	Analysis of synonymous codon usage in Hepatitis A virus	2011-04-16		.txt	text/plain	3215	164	51	In surprise, only A 3 % has a significant correlation with both principle axes which represent the major trend in codon usage variation, suggesting that nucleotide A is the major factor influencing the synonymous codon usage pattern of HAV genome. Despite the ratio of U 3 % was the highest, the major compositional constraint, which shaping the synonymous codon usage pattern of HAV genome, was from the percent of nucleotide A on the third codon position (Table 4) . This discovery was different from many reports which suggest that C+G compositional constraints were the major factor influencing codon usage bias in virus genome [18, 29, 30] . Mutational pressure and natural selection are generally thought to be the main factors that account for codon usage variation between genes in different Table 3 Summary of correlation analysis between the A, U, C, G contents and A 3 , U 3 , C 3 , G 3 organisms [14] [15] [16] [17] [18] [19] [20] [21] .	./cache/cord-274375-a11ztdpg.txt	./txt/cord-274375-a11ztdpg.txt