adenineThe base A, found across from T on the other strand. In RNA, adenine pairs with uracil.
base pairOne rung of the ladder: A with T, or C with G. The two bases of a base pair are held together by hydrogen bonds.
cytosineThe base that joins guanine with three hydrogen bonds. Cytosine is written C. It is found in both DNA and RNA.
deoxyriboseThe five-carbon sugar in each nucleotide of DNA. The name deoxyribonucleic acid comes from this sugar.
DNAThe molecule that holds an organism's inherited information. DNA is short for deoxyribonucleic acid.
double helixA twisted ladder: two long chains spiraling together. The double helix is the shape of a DNA molecule.
guanineThe two-ring base written with the letter G. Guanine is found in both DNA and RNA.
hydrogen bondA weak attraction that holds the two strands together. Hydrogen bonds join the two bases of each base pair.
nucleotideThe three-part unit that a DNA strand is built from. A strand of DNA is a long chain of nucleotides.
phosphate groupPhosphorus and oxygen atoms that join sugar to sugar. Sugars and phosphate groups alternate along the backbone of each strand.
strandA single chain of nucleotides; DNA has two. In a DNA molecule the two strands point opposite ways.
thymineThe pyrimidine base found in DNA but not in RNA. Thymine is written T.
Show all 36 terms (24 more)
DNA replication 12
DNA ligaseThe enzyme that joins pieces of DNA into one strand. DNA ligase links the Okazaki fragments together.
DNA polymeraseThe enzyme that adds nucleotides to a growing strand. DNA polymerase adds one nucleotide at a time.
helicaseThe enzyme that unwinds DNA and pulls its strands apart. Helicase opens the double helix at the replication fork.
lagging strandThe new strand made in sections, away from the fork. The lagging strand is built from many primers, not one.
leading strandThe new strand made in one piece, toward the fork. The leading strand grows in the same direction as the replication fork.
Okazaki fragmentOne short piece of new DNA, later joined to others. Okazaki fragments form on the lagging strand.
primaseThe enzyme that lays down a short RNA primer. Primase is a kind of RNA polymerase.
primerA short piece of nucleic acid where copying starts. DNA polymerase extends a new strand from a primer.
replicationThe doubling of DNA so each new cell gets a copy. Replication makes two DNA molecules from one.
replication forkThe Y-shaped place where the two strands separate. New DNA is made at the replication fork.
semiconservativeKeeping one old strand in each new DNA molecule. After semiconservative replication, each DNA molecule has one parent strand and one new strand.
templateAn existing strand that sets the order of a new one. Each of the two parent strands is a template.
Bases and RNA 12
complementaryDescribes bases or strands that pair up, as A does with T. Opposite the bases ATTGC, the complementary strand has TAACG.
geneA length of DNA handed down as one unit of inheritance. A gene is copied into RNA by transcription.
messenger RNAThe RNA copy of a gene that a ribosome reads. Messenger RNA is written mRNA for short.
nitrogenous baseThe nitrogen-rich part of a nucleotide, such as A or G. The five main nitrogenous bases are A, C, G, T and U.
nucleic acidA polymer of nucleotides, such as DNA or RNA. Nucleic acids are found in all cells and in viruses.
polymerA giant molecule: one small unit linked over and over. DNA is a polymer, and its repeating units are nucleotides.
purineAny base with two fused rings, such as adenine. The two purines in DNA and RNA are adenine and guanine.
pyrimidineAny base with a single ring, such as cytosine or uracil. The pyrimidines are cytosine, thymine and uracil.
riboseThe sugar with one more oxygen atom than deoxyribose. Ribose is a simple sugar with five carbon atoms.
RNAThe nucleic acid whose sugar is ribose. RNA is short for ribonucleic acid. Its four bases are A, U, C and G.
transcriptionThe step in which a cell writes a gene out as RNA. The RNA copy carries the sequence of the gene.
uracilThe RNA-only base, written U, that pairs with A. Uracil is written U. It pairs with adenine.
How this list was compiled: Term list chosen for this site on 2026-10-09. Each meaning is written in our own words and was checked that day against the English Wikipedia article on the term (https://en.wikipedia.org/), whose text is under the Creative Commons Attribution-ShareAlike license: DNA, Nucleic acid double helix, Nucleotide, Base pair, Adenine, Thymine, Cytosine, Guanine, Deoxyribose, Phosphate, Hydrogen bond, DNA replication (strand, template, leading strand, lagging strand, replication fork), Helicase, DNA polymerase, Primase, Primer (molecular biology), DNA ligase, Okazaki fragments, Semiconservative replication, RNA, Ribose, Uracil, Messenger RNA, Transcription (biology), Purine, Pyrimidine, Complementarity (molecular biology), Nucleic acid, Nucleotide base, Gene and Polymer. Each was checked a second time against the entry for the term in Wiktionary, the free dictionary (https://en.wiktionary.org/), under the same license, and DNA, double helix, nucleotide, base pair, adenine, thymine, cytosine, guanine, replication, primer, uracil, messenger RNA, transcription, gene and nucleic acid against the Talking Glossary of Genomic and Genetic Terms of the U.S. National Human Genome Research Institute (https://www.genome.gov/genetics-glossary). The example after each meaning is our own. Licence: own work
How it works
A DNA vocabulary worksheet in three sets of twelve: the structure of DNA, DNA replication, and the bases and RNA. Each set prints as a matching sheet, terms on the left and meanings on the right in another order, and the answer key comes last.
Read the full guide
A DNA replication vocabulary worksheet
In Set, DNA replication prints replication, helicase, DNA polymerase, primase, primer, DNA ligase, template, leading strand, lagging strand, Okazaki fragment, replication fork and semiconservative.
A DNA and RNA vocabulary worksheet
Bases and RNA has RNA, ribose, uracil, messenger RNA, transcription, purine, pyrimidine, complementary, nucleic acid, nitrogenous base, gene and polymer. The set the page opens on, DNA structure, has the DNA vocabulary words met first: the double helix, the nucleotide and its three parts, the four bases and the hydrogen bond.
Codon, anticodon and translation are left out: the three sets stop at transcription.
Questions and answers
What are the four bases of DNA?
Adenine (A), thymine (T), cytosine (C) and guanine (G). A pairs with T, and C pairs with G. In RNA, uracil (U) takes the place of thymine.
What is the difference between DNA and RNA?
The sugar in DNA is deoxyribose; the sugar in RNA is ribose, which has one more oxygen atom. DNA has the base thymine where RNA has uracil. DNA is a double helix of two strands, and messenger RNA is a single strand.
What does semiconservative replication mean?
Each new DNA molecule keeps one strand of the parent molecule and gains one new strand. Helicase separates the two parent strands, and each one is the template for its new partner.
Is there a DNA vocabulary worksheet PDF?
The page has no PDF file to download. Print worksheet opens the print window of your browser, and Save as PDF there keeps the sheet and its answer key as one file.