if the expression level of each pair of autosomes ( gray for both males and females ) is set to 1.0 , then the expression level of the two x chromosomes in females ( pink ) and the single x chromosome in males ( blue ) is also equal to 1.0 . to achieve this dosage compensation , the single x chromosome in the drosophila male soma and germline , c. elegans male soma , and mammalian male soma is upregulated ( dark blue , up - arrow ) . in drosophila female soma , the x chromosomes are both expressed and thus not upregulated ( light pink ) . according to gupta et al . , each x chromosome in the drosophila female germline is probably upregulated , and yet they must also be downregulated somehow , in order to prevent functional tetrasomy ( light pink , double arrow ) . the x chromosomes in c. elegans hermaphrodite soma are presumably upregulated , but they are also known to be downregulated by half ( light pink , double arrow ) . in mammalian females , one of the two x chromosomes is active and upregulated ( dark pink , up - arrow ) , while the other x chromosome gets inactivated ( white , down - arrow ) . the haploid germ cells of mammals express but do not upregulate their x chromosomes to achieve the same level of autosomal expression ( 0.5 ; light pink for female and light blue for male ) . primary mammalian oocytes , which have two non - upregulated x chromosomes , and spermatocytes , in which the x chromosome is largely silenced , are not depicted .
dosage compensation equalizes gene dosage between males and females , but its role in balancing expression between the x chromosome and the autosomes may be far more important . 
 now , dna microarrays have shown equality between the average expression of x - linked genes and that of autosomal genes , in male and female tissues of flies , worms and mice .