degeneration. deterioration; change from a higher to a lower form, especially change of tissue to a lower or less functionally active form. When there is chemical change of the tissue itself it is true degeneration; when the change consists in the deposit of abnormal matter in the tissues, it is infiltration.apetoretinal degeneration degeneration of the pigmented layer of the retina. transneuronal degeneration atrophy of certain neurons after interruption of afferent axons or death of other neurons to which they send their efferent output.
There are four different DNA nucleotides, each defined by a specific nitrogenous base: adenine (often abbreviated A in science writing), thymine (abbreviated T), guanine (abbreviated G), and cytosine (abbreviated C) (Figure 2).
Nucleotides Nucleotides are the monomers, building blocks, of nucleic acids (DNA and RNA). Each nucleotide includes three components: a phosphate, a sugar, and a nitrogenous b â¦ ase. The phosphate is bonded to the sugar through phosphodiester bonds and makes up the backbone of the molecule.here are four available nitrogenous bases in a DNA's nucleotides: adenine, thymine, guanine, and cytosine. RNA nucleotides feature the same bases with the exception of uracil, which replaces thymine.