Patterns of gene co-expression are sometimes conserved over substantial timescales, despite significant turnover in the associated transcription factors and chromatin organisation.
In particular, these analyses show that if two genes are coexpressed in one organism, then their orthologs also tend to be coexpressed in other organisms, i.e. coexpression is sometimes conserved.
Conservation sometimes conserves more than we realize.
After a few hours, as he sat calmly and felt no symptoms, he realized that the bite was what herpetologists refer to as a dry bite -- cobras sometimes conserve their venom.
Other conservation laws, in particular linear and quadratic Casimirs and momenta, can sometimes be conserved too, depending on the details of the equations under consideration and the form of discretization employed.
Potassium must sometimes be conserved also, but, as the amount of potassium in the blood plasma is very small and the pool of potassium in the cells is about thirty times as large, the situation is not so critical for potassium.
Our findings are also consistent with a growing body of evidence that developmental enhancers, while sometimes deeply conserved throughout evolution [37], [38], can be quite dynamic in terms of their genomic position and sequence content [39], [40].
On the other hand, it is known that cis-acting regulators of splicing are sometimes not conserved in sequence between orthologous genes [ 19] or are not located at orthologous positions [ 20], but still can preserve their function.
These insights raise exciting questions about the mechanisms of evolutionary change that underlie the development of morphological diversity, including why convergently evolved nervous systems sometimes use highly conserved suites of genes, and what developmental constraints govern variations in these mechanisms across animals.
However the S of NIKS is not 100% conserved, sometimes present as L, N or D. The only exceptions to the NIK amino acids of the motif are the eRF1s of ciliates as previously reported [ 40, 42].
Indeed, the broader developmental significance of bldA may not extend beyond Streptomycineae, as in non- Streptomycineae genomes TTA codons do not show the positional bias towards the start of genes that is observed in streptomycetes, and sometimes occur in conserved growth-associated genes (Chater & Chandra, 2008).
