The glial cells outnumber theneurones and the two cell types occupy a comparable amount of space in nervous tissue. The main glial cell types are, inthe central nervous system, astrocytes and oligodendrocytes and, in the peripheral nervous system, Schwann cells, entericglial cells and satellite cells.he glial cells outnumber theneurones and the two cell types occupy a comparable amount of space in nervous tissue. The main glial cell types are, inthe central nervous system, astrocytes and oligodendrocytes and, in the peripheral nervous system, Schwann cells, entericglial cells and satellite cells.
1 Cytosine is found in both DNA and RNA, but thymine is only found in DNA and uracil is only found in RNA.  A nucleotide is formed when a phosphate attahes to the 5' carbon of the sugar and one of the nitrogenous baseses attaches to the 1' carbon of the sugar.
1 DNA and RNA base pairing is slightly different, since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. 2  Uracil differs from thymine in that it lacks a methyl group on its ring. DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. 2  The only difference between ribose and deoxyribose is that ribose has one more-OH group than deoxyribose, which has-H attached to the second (2') carbon in the ring.