8. The Control of Gene Expression: Key Terms

• Acetylation**:** The addition of acetyl groups to histones, making genes more accessible to transcription factors and activating them.

• Addition**:** A gene mutation where one or more nucleotide bases are inserted into a DNA sequence, often causing a frameshift to the right.
• Benign**:** A non-cancerous tumour that grows slowly, is confined to a capsule, and remains in its original location. These are often removable via surgery.

• Cancer**:** A non-communicable disease caused by tumour cells that can spread to other parts of the body (metastasise).
• Cellular proteome**:** The complete set of proteins expressed in a specific type of cell.
• Complementary DNA (cDNA)****: A single strand of DNA that is complementary to an mRNA template strand.
• Complete proteome**:** All the proteins encoded by an organism's genome.
• Deletion**:** A gene mutation where one or more nucleotide bases are removed from a DNA sequence, often causing a frameshift to the left.
• Differentiation**:** The process by which cells become specialised to perform specific functions.
• DNA hybridisation**:** Combining single-stranded DNA with a complementary fragment of DNA or RNA.
• DNA ligase**:** An enzyme that joins DNA fragments by sealing the sugar-phosphate backbone.
• DNA polymerase**:** An enzyme that builds a double-stranded DNA molecule by adding complementary nucleotides to a template strand.
• DNA probe**:** A labelled, single-stranded DNA segment used to identify specific alleles or genes.
• DNA sequencing**:** Determining the nucleotide base sequence of an organism's DNA.
• Duplication**:** A mutation where one or more nucleotide bases are repeated, potentially causing a frameshift to the right.
• Epigenetics**:** The study of gene expression changes not caused by alterations in the DNA sequence.
• Frameshift mutation**:** A mutation caused by addition or deletion of bases that alters all subsequent triplet codes, often producing non-functional proteins.
• Gel electrophoresis**:** A technique that separates DNA fragments by size using an electric current.
• Gene machine**:** A method for synthetically creating genes using a computer to design base sequences.
• Gene mutation**:** A change in one or more nucleotide bases or their arrangement in DNA, occurring spontaneously and potentially altering the genotype.
• Gene therapy**:** Inserting a functional gene from a healthy individual into cells lacking that gene to treat genetic conditions.
• Genetically modified organism (GMO)****: An organism whose genome has been altered.
• Genetic counselling**:** Providing advice and information to individuals or families at risk of genetic disorders to help with decision-making.
• Genetic fingerprinting**:** A technique for identifying organisms based on DNA patterns, with applications in forensics, paternity testing, and species identification.
• Genetic screening**:** Testing individuals for specific faulty alleles to detect genetic conditions.
• Genome**:** The complete set of genetic material in an organism.
• Hypermethylation**:** Excessive methylation of DNA, leading to inactivation of tumour suppressor genes and tumour formation.
• Hypomethylation**:** Reduced methylation of DNA, activating oncogenes and promoting tumour formation.
• Induced pluripotent stem (iPS) cells**:** Unipotent cells reprogrammed into pluripotent stem cells capable of self-renewal.
• Inversion**:** A mutation where nucleotide bases break off from a DNA sequence and reattach in reverse order.
• In vitro**:** A process conducted outside a living organism in a controlled environment, such as amplifying DNA using PCR.
• In vivo**:** A process carried out within a living organism, such as inserting DNA fragments into host cells for amplification.
• Malignant**:** A cancerous tumour that grows rapidly, lacks a capsule, and can spread to other body regions, requiring treatments like surgery, chemotherapy, or radiotherapy.

• Marker genes**:** Genes inserted into plasmids to identify cells that have taken up desired DNA, often providing fluorescent markers or antibiotic resistance.
• Metastasis**:** The spread of cells from a primary tumour to other parts of the body, forming secondary tumours.
• Methylation**:** The addition of methyl groups to cytosine bases in DNA, which inhibits transcription by making DNA less accessible or blocking transcription factors.
• Multipotent cells**:** Stem cells in mature mammals that can differentiate into a limited number of related cell types.
• Mutagenic agent**:** A factor that increases the rate of mutations, such as chemicals or radiation.
• Mutation**:** A random change in DNA that may result in genetic variants.
• Mutation rate**:** The frequency of mutations per biological event, such as per cell division.
• Non-coding DNA**:** DNA that does not encode proteins but regulates gene expression.
• Oestrogen**:** A steroid hormone that activates transcription by binding to a receptor on transcriptional factors.
• Oncogenes**:** Mutated proto-oncogenes that become continuously active, promoting uncontrolled cell division.
• Personalised medicine**:** Tailored healthcare treatments based on an individual's genetic profile.
• Pluripotent cells**:** Embryonic stem cells capable of differentiating into almost any cell type.
• Polymerase Chain Reaction (PCR)****: An in vitro technique to rapidly amplify DNA fragments.
• Primers**:** Short nucleotide sequences complementary to the ends of DNA fragments, used in PCR.
• Promoter**:** A DNA region where RNA polymerase binds to initiate transcription.
• Proto-oncogenes**:** Genes that stimulate cell division in response to growth factor signals.
• Recognition sequences**:** Specific DNA sequences where restriction enzymes cut.
• Recombinant DNA**:** DNA formed by combining genetic material from two different organisms.
• Recombinant DNA technology**:** Techniques used to transfer DNA from one organism to another.
• Restriction endonucleases**:** Enzymes that cut DNA at specific sequences, creating sticky ends.
• Reverse transcriptase**:** An enzyme that synthesises DNA from an RNA template.
• Risk factor**:** A variable associated with an increased likelihood of disease or infection.
• RNA interference (RNAi)****: A mechanism for silencing gene expression by degrading target mRNA, preventing translation.
• Silent mutation**:** A substitution mutation that does not change the amino acid sequence due to the genetic code's degeneracy.
• Stem cells**:** Unspecialised cells capable of dividing and differentiating into various cell types.
• Sticky ends**:** Overhanging single-stranded DNA created by restriction enzymes.
• Substitution**:** A mutation where one nucleotide base is replaced with another.
• Terminator**:** A DNA region where RNA polymerase stops transcription and is released.
• Thermocycler**:** A machine used in PCR to control temperature changes at specific time intervals.
• Totipotent cells**:** Early embryonic stem cells capable of forming any body cell type.
• Transformation**:** The introduction of plasmids into bacterial cells to create transgenic bacteria.
• Tumour**:** An abnormal cell mass resulting from uncontrolled cell division.
• Tumour suppressor genes**:** Genes that regulate cell division, repair DNA, and trigger apoptosis in damaged cells.
• Transcriptional factors**:** Molecules that bind to specific DNA sequences to regulate transcription.
• Transgenic organism**:** An organism containing recombinant DNA from another species.
• Translocation of bases**:** A mutation where nucleotide bases detach from one chromosome and attach to another.
• Unipotent cells**:** Stem cells that can differentiate into a single cell type, derived from multipotent cells.
• Variable number tandem repeats (VNTRs)****: Repeated non-coding DNA sequences, unique to individuals.
• Vector**:** A carrier (e.g., plasmid) used to transfer genetic material into another organism.
• Whole-genome shotgun (WGS) sequencing**:** A method for sequencing entire genomes by cutting DNA into fragments and using algorithms to align overlapping sections.