topic 8

• 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.
• Variation: The differences between individuals due to genes, the environment or a combination of both.
• 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.
• Cancer: A non-communicable disease resulting from tumour cells that metastasise.
• Cellular proteome: The proteins expressed in a given type of cell.
• 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 counselling: A service that provides information and advice to people affected by or at risk of genetic diseases. This helps individuals and families to make informed decisions.
• 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.
• Hypomethylation: Reduced methylation of DNA. This results in the activation of oncogenes 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.
• Inversion: A form of gene mutation in which a group of nucleotide bases ‘break off’ from the DNA sequence and reattach in the same position but in the reverse order.
• 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.
• Malignant: Describes a tumour that is cancerous. Such tumours grow rapidly, are not enclosed in a capsule and can spread to other regions of the body. Treatment involves radiotherapy, chemotherapy or surgery.
• 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.
• Metastasis: The process by which cells break off from a primary tumour and spread to other areas of the body, forming secondary tumours.
• Methylation: The transfer of methyl groups to cytosine bases of DNA. Methylation inhibits transcription by making the DNA less accessible to transcriptional factors or preventing transcriptional factors from binding. This deactivates the gene.
• Multipotent cells: Stem cells found in mature mammals that can only differentiate into a limited number of cell types (specific to a tissue).
• Mutagenic agent: An agent that increases the rate of gene mutations above normal level.
• Mutation: A random change in DNA which may result in genetic variants.
• Mutation rate: The frequency of mutations per biological unit (e.g. per cell division).