These libraries can be from different samples, experiments and/or organisms, and cross-contamination could arise in sequencing in such studies.
Chapter 2, "Fallible Design," concerns the problems that can arise in coding sequences of DNA.
Although they arise in anonymous sequences, ENCs gradually incorporate repetitive arrays.
In vertebrates, new miRNAs tend to arise in intronic sequences (Campo-Paysaa et al. 2011; Meunier et al. 2013), and so miRNA genes nested in the introns of other genes might be younger and show faster sequence evolution than miRNAs located in intergenic regions.
It is unclear how frequently similar problems will arise in the sequencing and analysis of other bacterial genomes, but it is worth noting that at least in A. actinomycetemcomitans massive variation in genome structure between strains can lead to confusion in some kinds of analyses.
On the other hand, though binding sites can arise in regulatory sequences as a result of the action of positive selection [ 19- 21] or through genetic drift alone [ 22], I show that an increase in binding affinity on average is not expected in the absence of selection.
Another caveat to the logic that argues genes with substantial divergence are likely to have their own function, is that substantial sequence divergence could arise in redundant gene sequences via occasional interparalog exchange that would not necessarily introduce frameshift, and other inactivating mutations.
The sets of roots arise in a definite sequence, in contrast to the more or less irregularly produced roots of all other extant lower vascular plants.
In mammals, the basic framework of the network is engineered during development from a sheet of neuroepithelial progenitors that arise in an anteroposterior sequence as the body plan unfolds.
In addition to demographic effects, an excess of singletons can arise, in principle, from sequencing error.
