Control of Gene Expression

• Acetylation: The addition of acetyl groups to histones. Acetylation activates the gene by making it more accessible to transcription factors.
• Addition: A form of gene mutation in which one or more nucleotide bases are inserted into a DNA sequence. This may result in a frameshift to the right.
• Benign: Describes a tumour that is non-cancerous. Such tumours grow slowly, are enclosed in a capsule and remain at the site of origin. They can usually be removed by surgery.
• Complementary DNA (cDNA): A single strand of DNA complementary to the mRNA template strand.
• Complete proteome: All of the proteins coded for by the genome.
• Deletion: A form of gene mutation in which one or more nucleotide bases are removed from a DNA sequence. This may result in a frameshift to the left.
• Differentiation: A process in which cells become specialised for function.
• DNA hybridisation: The process by which a single-stranded segment of DNA is combined with a complementary fragment of DNA or RNA.
• DNA ligase: An enzyme that joins the sugar-phosphate backbone of two DNA segments.
• DNA polymerase: An enzyme that synthesises a double-stranded molecule of DNA from a single template strand using complementary nucleotides.
• DNA probe: A short, single-stranded segment of DNA that can be fluorescently or radioactively labelled. DNA probes are used to locate specific alleles of genes.
• DNA sequencing: Determining the entire DNA nucleotide base sequence of an organism.
• Duplication: A form of gene mutation in which one or more nucleotide bases are repeated. This may result in a frameshift to the right.
• Epigenetics: The study of changes in gene expression that are not due to alterations in the nucleotide base sequence of DNA.
• Frameshift mutation: A form of gene mutation in which the addition or deletion of nucleotide bases alters all subsequent triplet codes in a DNA sequence. This often leads to the production of a non-functional protein.
• Gel electrophoresis: A technique that separates fragments of DNA by size using electric current.
• Gene machine: A method of artificially manufacturing genes by feeding the desired sequence of bases into a computer.
• Gene mutation: A change to at least one nucleotide base in DNA or the arrangement of bases. Gene mutations occur spontaneously and may result in changes to genotype.
• Gene therapy: A technique in which a functional gene, cloned from a healthy individual, is inserted into cells that lack the gene.
• Genetically modified organism (GMO): An organism that has had its genome altered.
• Genetic fingerprinting: A technique used to genetically identify an organism. It has applications in forensics, paternity testing, diagnostics and the breeding of plants and animals.
• Genetic screening: Testing individuals for certain faulty alleles.
• Genome: The complete genetic material of an organism.
• Hypermethylation: Increased methylation of DNA. This results in the inactivation of tumour suppressor genes and the resulting formation of tumours.
• Induced pluripotent stem (iPS) cells: Unipotent cells that have been reprogrammed (using transcriptional factors) to become pluripotent stem cells. iPS cells are capable of self-renewal.
• In vitro: Describes a procedure that takes place outside of a living organism in a controlled environment e.g. DNA is amplified using PCR in a thermocycler.
• In vivo: Describes a procedure that takes place inside of a living organism e.g. fragments of DNA can be transferred to a host cell (using a vector) where they are amplified.
• Marker genes: An additional gene inserted into a plasmid that is used to aid in the identification of host cells that have taken up the desired gene. Marker genes are easily recognisable e.g. fluoresce or provide antibiotic resistance.
• Multipotent cells: Stem cells found in mature mammals that can only differentiate into a limited number of cell types (specific to a tissue).
• Non-coding DNA: DNA that does not code for a protein but instead controls gene expression.
• Oestrogen: A steroid hormone involved in the initiation of transcription. It joins to a receptor site on a transcriptional factor, activating the DNA binding site and stimulating transcription.
• Oncogenes: Mutations of proto-oncogenes that are activated continuously.
• Personalised medicine: A form of medical care that enables doctors to provide healthcare customised to an individual's genotype.
• Pluripotent cells: Stem cells found in embryos that have the ability to differentiate into almost all types of cell.
• Polymerase Chain Reaction (PCR): An in vitro technique used to rapidly amplify fragments of DNA.
• Primers: Short nucleotide sequences, complementary to one end of each of the DNA fragments.
• Promoter: Region of DNA where RNA polymerase binds during transcription.
• Recombinant DNA technology: The process by which segments of DNA are transferred from one organism to another.
• Restriction endonucleases: Enzymes that cut DNA molecules at recognition sequences creating sticky ends.
• Reverse transcriptase: An enzyme that synthesises DNA from RNA.