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Genetic material

Material used to store genetic information in the nuclei or mitochondria of an organism's cells



In nucleic acid chemical nomenclature, a nucleoside covalently linked to one or more phosphate groups. Nucleotides containing a single phosphate linked to the 59 carbon of the ribose or deoxyribose are the building blocks of nucleic acids.


Nitrogenous bases

Nitrogen-containing molecule that has the same chemical properties as a base. Building blocks of DNA & RNA; Adenine, Guanine, Cytosine, Thymine, & Uracil


Antisense RNA

An RNA molecule (synthesized in vivo or in vitro) with a ribonucleotide sequence that is complementary to part of an mRNA molecule.



Ribonucleic acid


Hydrogen bond

Holds the nucleotides together. Chemical bond where a hydrogen atom of one molecule is attracted to an electronegative atom, such as nitrogen, oxygen, or fluorine atom


Discontinuous synthesis

The synthesis of DNA in discontinuous fragments on the lagging strand during replication. The fragments, known as Okazaki fragments, are subsequently joined by DNA ligase to form a continuous strand.


Double helix

The model for DNA structure proposed by James Watson and Francis Crick, in which two antiparallel hydrogen-bonded polynucleotide chains are wound into a right-handed helical configuration 2 nm in diameter, with 10 base pairs per full turn.


Base pairing

Adenine with thymine. Guanine with cytosine



Purines include a number of biologically important compounds, such as adenosine, caffeine, uric acid, and the two bases adenine and guanine, which are components of DNA and RNA.



The pyrimidine nitrogenous bases are derived from the organic compound pyrimidine through the addition of various functional groups. The three pyrimidines are thymine which is only found in DNA, uracil which is only found in RNA, and cytosine which is found in both DNA and RNA.


DNA replication

DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. Replication is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, as the parent cell.


Semiconservative replication

A mode of DNA replication in which a double-stranded molecule replicated in such a way that the daughter molecules are each composed of one parental and one newly synethized strand


DNA polymerase

RNA polymerase is an enzyme that is responsible for copying a DNA sequence into an RNA sequence, duyring the process of transcription. As complex molecule composed of protein subunits, RNA polymerase controls the process of transcription, during which the information stored in a molecule of DNA is copied into a new molecule of messenger RNA.



Primase is an enzyme that synthesizes short RNA sequences called primers. These primers serve as a starting point for DNA synthesis. Since primase produces RNA molecules, the enzyme is a type of RNA polymerase.



An enzyme that utilizes energy from nucleoside triphosphate (e.g. ATP) hydrolysis in order to unwind the two annealed nucleic acid strands (e.g. DNA) Supplement.


Replication origin

The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated. This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses.


RNA primer

In nucleic acids, a short length of RNA or single-stranded DNA required for initiation synthesis directed by polymerases



The heavily staining, late-replicating regions of chromosomes that are prematurely condensed in interphase.


Long interspersed elements (LINEs)

Long, repetitive sequences interspersed in the genomes of higher organisms


Okazaki fragment

The short, discontinuous strands of DNA produced on the lagging strand during DNA synthesis



The theory that each gene is responsible for the synthesis of a single polypeptide. It was originally stated as the one gene-one enzyme hypothesis by the US geneticist George Beadle in 1945 but later modified when it was realized that genes also encoded nonenzyme proteins and individual polypeptide chains.



RNA interference (antisense RNA). RNA silencing



A molecule composed of amino acids linked together by covalent peptide bonds. This term is used to denote the amino acid chain before it folds into its functional three-dimensional protein configuration


Reading frame

A linear sequence of codons in a nucleic acid.


Replication fork

The Y-shaped region of a chromosome associated with the site of DNA replication


Transcription factor

In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence.



The first (primary) transcript from a protein coding gene is often called a pre-mRNA and contains both introns and exons. Pre-mRNA requires splicing (removal) of introns to produce the final mRNA molecule containing only exons.


Mature mRNA

Messenger RNA (mRNA) is a large family of RNA molecules that convey genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression. RNA polymerase transcribes primary transcript mRNA (known as pre-mRNA) into processed, mature mRNA.


RNA processing

Any modification made to RNA between its transcription and its final function in the cell. These processing steps include the removal of extra sections of RNA, specific modifications of RNA bases, and modifications of the ends of the RNA.


5' capping

At the end of transcription, the 5' end of the RNA transcript contains a free triphosphate group since it was the first incorporated nucleotide in the chain. The capping process replaces the triphosphate group with another structure called the "cap". The cap is added by the enzyme guanyl transferase. This enzyme catalyzes the reaction between the 5' end of the RNA transcript and a guanine triphosphate (GTP) molecule.


3' poly(A) tail addition

The addition of a string of adenines. It is catalyzed by the enzyme poly (A) polymerase, which recognizes the sequence AAUAAA as a signal for the addition.



A term used to refer to the process by which the DNA of an organism is cut and a gene, perhaps from another organism, is inserted.


Template strand

Coding strand; the sequence of DNA that is copied during the synthesis of mRNA


Non-template strand

Non-coding strand; sequene corresponds to the codons that are translated into protein


Somatic cells

Body cells, so nonheritable


Genetic code

The genetic code is a set of rules defining how the four-letter code of DNA is translated into the 20-letter code of amino acids, which are the building blocks of proteins.


Initiator tRNA

A special methionine tRNA that binds to the initiation codon AUG that forms part of the initiation complex at the start of mRNA translation.



The derivation of the amino acid sequence of a polypeptide from the base sequence of an mRNA molecule in association with a ribosome and tRNAs


Amino acid

An amino acid is a type of organic acid that contains a carboxyl functional group (-COOH) and an amine functional group (-NH2) as well as a side chain (designated as R) that is specific to the individual amino acid. Amino acids are considered to be the building blocks of polypeptides and proteins.


Wobble hypothesis

An idea proposed by Francis Crick, stating that the third base in an anticodon can align in several ways to allow it to recognize more than one base in the codons of mRNA


Phosphodiester bond

In nucleic acids, the system of covalent bonds by which a phosphate group links adjacent nucleotides, extending from the 59 carbon of one pentose sugar (ribose or deoxyribose) to the 39 carbon of the pentose sugar in the neighboring nucleotide. Phosphodiester bonds create the backbone of nucleic acid molecules.


Stop codon

In the genetic code, a stop codon (or termination codon) is a nucleotide triplet within messenger RNA that signals a termination of translation into proteins. Proteins are based on polypeptides, which are unique sequences of amino acids.



In eukaryotes, a nuclear complex consisting of four pairs of histone molecules wrapped by two turns of a DNA molecule


Triplet codon

The standard version of the genetic code, in which a sequence of three nucleotides on a DNA or RNA molecule codes for a specific amino acid in protein synthesis.


Base pair

A base pair refers to two bases which form a "rung of the DNA ladder." A DNA nucleotide is made of a molecule of sugar, a molecule of phosphoric acid, and a molecule called a base. The bases are the "letters" that spell out the genetic code.


Chloroplast DNA

chloroplast-DNA (cp-DNA) Circular DNA, like that of mitochondria but several times larger, which is found in chloroplasts and other plastids and contains genes involved in the photosynthetic pathway. It is independent of nuclear DNA and is maternally inherited. Between 40 and 80 DNA molecules occur in each organelle.


Mitochondrial DNA

Circular DNA found in mitochondria that has only 37 genes, that of which are all maternal



A molecule composed of polymers of amino acids joined together by peptide bonds. It can be distinguished from fats and carbohydrates by containing nitrogen. Other components include carbon, hydrogen, oxygen, sulphur, and sometimes phosphorus.


Replication bubble/eye

An enzyme called helicase is used to separate these two strands. Like a zipper that has unzipped in the middle, the separated DNA strands form a little open pucker. This is the replication bubble. A replication bubble is an unwound and open region of a DNA helix where DNA replication occurs.


Restriction enzymes

An enzyme from bacteria that can recognize specific base sequences in DNA and cut the DNA at that site



Hutchinson-Gilford progeria syndrome is a genetic condition characterized by the dramatic, rapid appearance of aging beginning in childhood. Mutations in the LMNA gene result in the production of an abnormal version of the lamin A protein.


Continuous synthesis

On the lower leading strand, synthesis is continuous because extension of a single RNA primer occurs without interruption into the replication fork as it continues to open to the right.


DNA mismatch and repair

DNA mismatch repair (MMR) is a system for recognizing and repairing erroneous insertion, deletion, and mis-incorporation of bases that can arise during DNA replication and recombination, as well as repairing some forms of DNA damage


Bacterial DNA

Bacteria have a single, double-stranded circular chromosome that is located in the cytoplasm in a structure called the nucleoid. Bacteria also contain smaller circular DNA molecules called plasmids.


Virus DNA

A DNA virus is a virus that has DNA as its genetic material and replicates using a DNA-dependent DNA polymerase. The nucleic acid is usually double-stranded DNA (dsDNA) but may also be single-stranded DNA (ssDNA).


Chromatin structure

The substance distributed in the nucleus of a cell that condenses to form chromosomes during cell division. It consists mainly of DNA and proteins called histones.


Chromosome condensation

Chromosome condensation is the dramatic reorganisation of the long thin chromatin strands into compact short chromosomes that occurs in mitosis and meiosis.



Highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and playing a role in gene regulation.