The phrase "a strict core" is correct and usable in written English.
It can be used to refer to a fundamental or essential part of something that is rigid or unyielding in nature.
Example: "The organization has a strict core of values that all employees are expected to uphold."
Alternatives: "a rigid foundation" or "an inflexible essence".
As a recent alumna of Ithaca College, I can attest to a campus environment that boasts a liberal mindset while obstructing students from taking black, Asian or Latino studies courses through the implementation of a strict core curriculum, hiring too few people of color for tenure-track faculty positions and making no adjustments to the mental health program that would benefit students of color.
However, we included draft genomes, which by their nature are incomplete, and a strict core analysis may overlook genes that are present but not sequenced or annotated.
Even if a strict core of vertically inherited genes might be limited, our results clearly demonstrate the existence of a soft core of cellular components involved in different processes whose genes have similar histories and can therefore be used to trace back the evolutionary relationships among the organisms that carry them (Gribaldo and Brochier-Armanet 2006; Gribaldo and Brochier 2009).
Plurality-embedded quartet topologies of the strict core gene families were encoded in a matrix according to the method of Baum (1992) and Ragan (1992) used in an MP phylogeny search (MRP) using the September 2011 version of TNT (Goloboff et al. 2008) with the same settings as for gene family composition analysis.
The soft core consists of 3,051 HGCs and the strict core contains 1,702 HGCs.
The least conserved strict core HGC has 1,158 members (substitutions per site: 0.324).
If the strict core (HGC must be found in all genomes) was considered, the core-genome shrinks to 1,702 HGCs.
The density plots of the soft core and the strict core are colored green and red, respectively.
The strict core, defined as present in all 21 genomes, revealed 893 gene families of which 643 only had single homologs per genome.
Of the 1435 orthologs in our dataset, which correspond to the 1054 CyOGs identified by Mulkidjanian and co-workers, 931 are likewise present in our relaxed core gene set (i.e. in either the strict core, RCF or RCF1).
More directly, Nilsson et al. found strict core M1 glycan modification of the glycopeptide consisting of mucin domain residues 361 373 in human α-DG, a peptide that is directly N-terminal to the peptide on which the core M3 phospho-O-mannose-trisaccharide was mapped by Yoshida-Moriguchi and colleagues.
