Term | Definition |
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3’ (3 prime) | 3' refers to the end of a single-stranded nucleic acid chain to which a hydroxyl group (-OH) is attached to the 3'-carbon atom of the nucleotide.1 |
5’ (5 prime) | 5' refers to the end of a single-stranded nucleic acid chain to which a phosphate is attached to the 5'-carbon atom of the nucleotide.1 |
Capsid | The capsid is the protein shell of a virus that protects the genetic material while interacting with the host environment.2 Capsid proteins determine cell-type specificity.3 |
Chromosome | A chromosome is an organized package of DNA found in the nucleus of a cell. Humans have 23 pairs of chromosomes–22 pairs of numbered chromosomes, called autosomes, and one pair of sex chromosomes, X and Y.4 |
Codon | A codon is a sequence of three nucleotides that codes a specific amino acid. For DNA, there are four different nucleotides (A, T, C, or G) from which a codon can be composed.5 |
Endocytosis | A cellular process by which substances are brought into a cell. The substance is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material.6 |
Enhancer | An enhancer is an upstream regulatory DNA sequence that provides binding sites to regulatory proteins and can augment the activity of a promoter.7 |
Episome | Exogenous DNA that remains physically independent of the cell’s endogenous chromosome or complement of chromosomes.8 |
Ex vivo gene therapy | Harvesting and cultivating of patient cells in the laboratory. Cells are incubated with vectors carrying a corrective or therapeutic gene. Cells with the new genetic information are then transplanted back into the patient from whom they were derived.9 |
Gene editing | Removal, disruption or correction of faulty elements of DNA within the gene.10 |
Gene transfer (gene addition) | Addition of a functional copy of a missing gene or augmentation of a gene that is non-functional into target cells to produce more of a protein.10,11 |
Immunogenicity | The ability of a substance, such as an antigen or epitope, to trigger an immune response in the host.12 |
Intron | An intron is a portion of DNA that does not code for an amino acid.13 |
Inverted terminal repeats (ITRs) | ITRs are 145-bp sequences that frame the expression cassette.14 |
In vivo | Administration of a vector carrying the therapeutic genetic material to a live animal. The vector can be delivered by a variety of methods, including direct injection into the blood (intravenous injection) or by various organs by other physical means of administration (hypodermic injection, aerosol, intrathecal, etc.).9 |
Messenger RNA (mRNA) | Single molecule of RNA that works as a chemical map for a protein product.9 |
Nucleus | Membrane-bound organelle that contains the cell's chromosomes. Pores in the nuclear membrane allow for the passage of molecules in and out of the nucleus.15 |
Plasmid | An extrachromosomal, self-replicating piece of DNA. Plasmids are usually circular and transferable between cells.16 |
Promoter | Sequence of DNA, typically at the 5’ region, where regulatory elements such as transcription factors bind and initiate transcription of the associated gene.17 |
Proteasome | A large protease complex which selectively degrades proteins by proteolysis. The proteasome works in collaboration with ubiquitin–polymerization of ubiquitin serves as a degradation signal that transports the target proteins to the proteasome for degradation.18 |
Seroprevalence | The proportions of individuals within a population with an antibody to a serotype. Seroprevalence is measured in blood serum.19 |
Serotype | Group of closely related microorganisms distinguished by a characteristic set of antigens and detected by an antibody.9 |
Terminator sequence (Poly(A)) | The Poly(A) signal sequence acts as the transcription terminator, halting transcription once the transgene is fully transcribed.20 |
Transduction | Transfer of genetic material into the nucleus of a cell, such that elements of the newly transferred DNA are then expressed. This can be accomplished naturally by a virus or other vector or experimentally by augmenting the receptivity of the cell membrane of the recipient cell with chemicals or electricity.21 |
Transfer RNA (tRNA) | tRNAs act as adaptors between the mRNA and the amino acids during translation. The tRNA has an anticodon loop that binds to the complementary mRNA codon and also has a bound amino acid.22 |
Transgene | The transgene is the nucleic acid sequence encoding an artificially added gene.23 |
Tropism | The ability of a virus to infect a particular type of cell in the body.23 |
Vector | A gene therapy delivery vehicle, which encapsulates a therapeutic gene and delivers it to target cells. Vectors can be either virus-derived or non-viral.9 |