connective tissue Any supporting tissue that lies between other tissues and consists of cells embedded in a relatively large amount of extracellular matrix. Includes bone, cartilage, and loose connective tissue.
connexin   Protein component of gap junctions, a four-pass transmembrane protein. Six connexins assemble in the plasma membrane to form a connexon, or “hemichannel.” (Figure 19–25) connexon   Water-filled pore in the plasma membrane formed by a ring of six connexin protein subunits. Half of a gap junction: connexons from two adjoining cells join to form a continuous channel through which ions and small molecules can pass. (Figure 19–25) consensus nucleotide sequence A summary or “average” of a large number of individual nucleotide sequences derived by comparing many sequences with the same basic function and tallying up the most common nucleotides found at each position. (Figure 6–12) consensus sequence   Average or most typical form of a sequence that is reproduced with minor variations in a group of related DNA, RNA, or protein sequences. Indicates the nucleotide or amino acid most often found at each position. Preservation of a sequence implies that it is functionally important.
conservative site-specifc recombination A type of DNA recombination that takes place between short, specific sequences of DNA and occurs without the gain or loss of nucleotides. It does not require extensive homology between the recombining DNA molecules.
constant region   In immunology: region of an immunoglobulin or T cell receptor chain that has a constant amino acid sequence.
constitutive secretory pathway   Pathway present in all cells by which molecules such as plasma membrane proteins are continually delivered to the plasma membrane from the Golgi apparatus in vesicles that fuse with the plasma membrane. The default route to the plasma membrane if no other sorting signals are present. (Figure 13–63) contact-dependent signaling   Form of intercellular signaling in which signal molecules remain bound to the surface of the signaling cell and influence only cells that contact it.
contractile ring Ring containing actin and myosin that forms under the surface of animal cells undergoing cell division. Contracts to pinch the two daughter cells apart. (Figure 17–42) convergent extension Rearrangement of cells within a tissue that causes it to extend in one dimension and shrink in another. (Figure 21–50)
COPI-coated vesicles Coated vesicles that transport material early in the secretory pathway, budding from Golgi compartments.
COPII-coated vesicles Coated vesicles that transport material early in the secretory pathway, budding from the endoplasmic reticulum.
copy number variations (CNVs) A difference between two individuals in the same population in the number of copies of a particular block of DNA sequence. This variation arises from occasional duplications and deletions of these sequences.
cortex   The cytoskeletal network in the cortical region of the cytosol just beneath the plasma membrane.
coupled reaction   Linked pair of chemical reactions in which the free energy released by one serves to drive the other. (Figure 2–29) covalent bond Stable chemical link between two atoms produced by sharing one or more pairs of electrons.  (Panel 2–1, pp. 90–91)
CRE-binding (CREB) protein   Transcription regulator that recognizes the cyclic AMP response element (CRE) in the regulatory region of genes activated by cAMP. On activation by PKA, phosphorylated CREB recruits a transcriptional coactivator (CREB-binding protein; CBP) to stimulate transcription of target genes.
CRISPR A defense mechanism in bacteria using small noncoding RNA molecules (crRNAs) to seek out and destroy invading viral genomes through complementary base-pairing and targeted nuclease digestion.
crista (plural cristae) A specialized invagination of the inner mitochondrial membrane.