Nucleotide(s): the basic unit from which nucleic acids are formed. (Indge, 188) The molecules that make up DNA. (Kandel4, 46) The building blocks of DNA and RNA. (Brooker, 214) DNA molecules consist of multiple copies of a single basic unit, the nucleotide, which comes in four forms: adenine (A), thymine (T), guanine (G), and cytosine (C). (Watson, xi) The four small repeating units making up each strand in the double helix of DNA. On one strand of DNA, adenine pairs and "binds" only to thymine. On the other strand, guanine pairs and binds only to cytosine. The pairing of nucleotide bases at multiple points along their length holds the two strands of DNA together. (Kandel, 243) In biochemistry – a compound in which a "phosphate group" is linked to the "sugar." (Oxford) Made up of three components: a five-carbon sugar, this is either “ribose,” in the case of RNA, or “deoxyribose” in the case of DNA; a phosphate group; and a nitrogen-containing base. (Indge, 189)

Purine(s): one of the two chemical families of nucleotide bases found in a nucleic acid molecule. The important feature of a purine is that it contains two rings of "atoms." (Indge, 224) DNA needs a 2-ring structure attached to a 1-ring structure. Hence purine binds to pyrimidine. Stores inherited information for "protein synthesis." (Norman, 6/17/09) Editor's note - includes adenine and guanine.

Adenosine: a nucleotide made up of the purine base “adenine” linked to the sugar, “ribose.” (Lawrence) Found in living tissues in the form of nucleotides. In combination: "adenosine monophosphate," "adenosine diphosphate (ADP)," and "adenosine triphosphate (ATP)." (Oxford)

Pyrimidine(s): one of the two chemical families of nucleotide bases found in a nucleic acid molecule. The important feature of a pyrimidine is that it contains a single ring of atoms. (Indge, 225) Stores inherited information for protein synthesis. (Norman, 6/17/09) Editor’s note - includes cytosine and thymine.

Strand: formed by the linkage of nucleotides in a linear manner. (Brooker, 214) Has directionality based on the orientation of the “sugar” molecules within the strand. One end has a phosphate group while the other end has an ‘OH group.’ Contains a specific sequence of bases. The sequence is thymine-adenine-cytosine-guanine. Because the nucleotides within a strand are attached to each other by stable bonds, the sequence cannot shuffle around or become rearranged. Therefore, the sequence will remain the same over time, except in rare cases when “mutations” occur.  (Brooker, 213)

DNA Replication Strands: each strand is used as a template for a daughter strand. (Norman, 7/7/09) Replication of both strands occurs simultaneously and in only one direction. (Micklos, 40)

Daughter Strands: the newly made strands in DNA replication. (Brooker, G-10) Complementary to the template strands. (Lewis, 174)

Lagging Strand: a DNA strand made as a series of small “okazaki fragments" that are eventually connected to each other (by “DNA ligase”) to form a continuous strand. The synthesis of these DNA fragments occurs in the direction away from the "replication fork." (Brooker, G-20) Discontinuous replication (occurs along this strand) with the new strand beginning with the 3-prime end. Some segments are left out. (Norman 7/7/09)

Leading Strand: a DNA strand made in the same direction that the replication fork is moving. The strand is synthesized as one long continuous molecule. (Brooker, G-20) Continuous replication (occurs along this strand) with the new strand beginning with the 5-prime end. (Norman 7/7/09)

Parental Strands: the DNA strand that is used as a template for DNA replication. (Lewis, 174)

RNA Synthesis Strand: one strand of a DNA molecule is copied into a (strand of a "mRNA") molecule. (Lewis, 3)

Coding Strand: the name for the strand in "RNA transcription" that is not used as a template. (Lewis, 180) Also referred to as ‘mRNA-like strand.’

Template Strand: the DNA strand that is used as a template for RNA synthesis. (Lewis, 174)