The innermost zone of the cortex, zona reticularis, and the middle zone, zona fasciculata, synthesize and secrete glucocorticoids and adrenal androgens. 

TLS Online TPP Program

#Id: 3684

#Unit 2. Cellular Organization

The “introns early” hypothesis is the proposal that introns have always been an integral part of the gene.  Genes originated as interrupted structures, and those now without introns have lost them in the course of evolution.

TLS Online TPP Program

#Id: 3685

#Unit 2. Cellular Organization

The “introns late” hypothesis is the proposal that the ancestral protein-coding sequences were uninterrupted and that introns were subsequently inserted into them

TLS Online TPP Program

#Id: 3686

#Unit 2. Cellular Organization

Pathogenicity islands are a characteristic feature of pathogenic bacteria genomes.These are large regions (10 to 200 kb) that are present in the genomes of pathogenic species but absent from the genomes of nonpathogenic variants of the same or related species. 

TLS Online TPP Program

#Id: 3687

#Unit 2. Cellular Organization

Pathogenicity islands GC content often differs from that of the rest of the genome, and it is likely that these regions are spread among bacteria by a process of horizontal transfer.

TLS Online TPP Program

#Id: 3688

#Unit 2. Cellular Organization

Bacillus anthracis has two large plasmids (extrachromosomal DNA molecules), one of which has a pathogenicity island that includes the gene encoding the anthrax toxin.

TLS Online TPP Program

#Id: 3689

#Unit 2. Cellular Organization