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).
The basic unit of structure for a DNA molecule is the nucleotide. A nucleotide is composed of a phosphate, a deoxyribose sugar molecule, and a nitrogen-containing base (A, T, C, or G). The instructions carried on DNA are used to make proteins from amino acids in the cytoplasm. nucleotide is composed of a phosphate, a deoxyribose sugar molecule, and a nitrogen-containing base (A, T, C, or G). The instructions carried on DNA are used to make proteins from amino acids in the cytoplasm.