Last updated
01 Dec 2025
| Terms | Definition |
|---|---|
| Allele | A version of a gene. For a given location in a gene there can be multiple possible alleles, each with different variants in the DNA sequence that can lead to differences in gene expression – either normal variation or disease causing. Alleles can vary in how common they are between different groups of people. |
| Affectedness | See Variable expressivity |
| Amino acid | Amino acids are the basic building blocks, or subunits, of a protein. They are combined according to the instructions in genes to form different types of proteins. |
| Bioinformatician | A professional with dual qualifications or knowledge in both biology and software analysis & interpretation of data. In both clinical and research settings, bioinformaticians help design and manage pipelines for the analysis of DNA and RNA sequences, and other forms of genomic data. |
| Biological specimen | A sample collected from a living or deceased person or organism, to be analysed as a part of health care or research. In human genomics, common specimens include blood, saliva, cheek swabs (buccal swab), and tissue (for example, a biopsy of a tumour). |
| Cascade testing | Cascade testing is a clinical process whereby family members of an individual diagnosed with a genetic condition are informed, counselled and subsequently tested for the same condition. |
| Carrier | A person possessing a variant associated with a genetic condition, who does not show symptoms but can pass it on to their children. |
| Cell and gene therapies | Advanced treatments that work at the cellular or genetic level. They may add, remove or modify cells or genetic material to treat or prevent a condition. |
| Chromosome | A long, thread-like piece of DNA. Each chromosome carries many genes. Most people have 46 chromosomes: 22 pairs of chromosomes plus two sex chromosomes (normally XX in females and XY in males). This means most people have two copies of each gene (except males only have one copy of genes on the X and Y chromosomes). |
| Clinical geneticist | A medical doctor with specialist training in the field of genetics, including the genetic evaluation, testing, diagnosis, and management of patients. Clinical geneticists typically interact directly with patients, request genomic testing, and interpret results. |
| Clinical genetics | A field of speciality practice in medicine focused on the assessment, management and treatment of genetic conditions. |
| Coding regions | The parts of the genome that can be used to make an RNA template for a protein. Coding regions make up only about 1% of the human genome. |
| Deletion | A deletion, as it relates to genomics, is a genetic variation involving the loss of a segment of DNA. It can be small, involving a few bases, to a large segment of a chromosome. |
| DNA (Deoxyribonucleic acid) | DNA is a long molecule made up of a sequence of nucleotides connected together in a row. There are four types of DNA nucleotide, which are like the alphabet that genes are written in. DNA is double stranded with each nucleotide joined to a partner nucleotide on the other strand, and the two linked strands winding around each other like a twisted ladder to make a double helix shape. |
| DNA methylation | Methylation of DNA involves the addition of a methyl group (1 carbon and 3 hydrogen atoms) to a cytosine (C) base of the DNA. While this doesn’t change the actual DNA sequence, the relative bulk of the methyl group can inhibit expression of that gene. Higher rates of methylation can silence a gene’s expression altogether. This is a type of epigenetic change. |
| Dominant | A pattern of inheritance of a genetic trait. If an allele is dominant, then a person only needs one copy of that allele to have the associated trait or condition. |
| Duplication | A duplication, as it relates to genomics, is a genetic variation involving the reproduction of one or more copies of a segment of DNA. It can be small, involving a few bases, to a large segment of a chromosome. While duplications are an important part of adaptation and evolution, they can also be associated with disease. |
| Epigenetics | Study of how external factors (such as diet, stress, lifestyle and environmental factors) can affect how our genes work. These effects don’t change gene sequences, but rather the levels at which genes are expressed and how they are expressed, thereby influencing health and disease. One type of epigenetic modification to the genome is called DNA methylation. Epigenetic changes can be influenced by environment and lifestyle. |
| Exome | The complete set of coding regions in the genome. |
| Family history | Family history, as it relates to genomics, involves tracing the patterns of traits and disease through a person’s bloodline. It can help inform a person’s risk of inheriting or developing a genetic condition. |
| Gene | A section of DNA that contains the instructions for a specific protein or function in the body, and so influences how the body grows, develops and functions. It is considered the basic unit of inheritance, passed from parents to their children. |
| Gene expression | The process by which information from a gene is used to make a protein or carry out a function. To make a protein first the DNA sequence of the gene is ‘expressed’ to make an RNA template (transcription), then the RNA template is used to build the protein (translation). Gene expression testing looks at RNA to examine, for example: how much a gene is expressed, which tissues it is being expressed in and whether the patient has a fusion gene variant or alternative splicing variant. |
| Gene panel | A collection of genes that are known to be associated with given condition(s) or disease presentation, which are used for genomic analysis to inform clinical management. |
| Genetic counsellor | An allied health professional with certified dual speciality training in genetics and counselling. They guide and support individuals and families impacted by or undergoing genetic testing, including areas such as informed decision-making, understanding genetic predisposition and the medical and psychological impacts of genetic testing results. |
| Genetic pathologist | A medical doctor with specialist training in genetics and genomics, and its contribution to health and disease. Genetic pathologists provide supervision, interpretation and clinical guidance in pathology laboratories during the process of selecting, conducting and reporting genetic tests, including communicating with wider patient health care teams. |
| Genetic testing (medical) | A laboratory test that looks at DNA or RNA to identify genetic variants that are relevant to health and disease. There are many different contexts or reasons for undergoing genetic testing, such as to diagnose or investigate a suspected genetic condition, inform reproductive planning for families, or seek targeted treatment options for conditions like cancer. Some types of genetic and genomic tests are described here. |
| Genetics | The study of genes and their role in inheritance and disease. When contrasted against genomics, genetics refers specifically to the study of single genes. |
| Genome | The complete set of genetic information within an organism’s cell. In humans this includes all the DNA in the cell’s nucleus, as well as the small chromosome in the mitochondria in the cell. |
| Genomics data | Health genomics information or data is an umbrella term that can encompass multiple types of outputs and information generated from genomic tests, depending on the context. These data can range in size, utility and sensitivity depending on the type of genomic testing conducted. Levels of data can range from the raw sequencing files generated during testing, to only the final testing results or classified variants reported. |
| Genomic information | Genomic data that has been analysed, interpreted and provides meaningful insights. |
| Genomic information management | Processes and/or systems that support the storage, use, management and sharing of genomic data and information and related health information. |
| Genomic medicine | The use of genomic information as part of assessment, management, prevention and treatment of patients who are at risk, suspected of or known to have a genetic or genomic condition. |
| Genomic sequencing | Genomic sequencing is a laboratory process that reads the order of nucleotides in DNA. This can involve sequencing a single gene, a panel of genes, the exome or the whole genome. Sequencing can also be used to look at gene expression, by converting RNA to DNA and sequencing that. Sequencing results help identify variants that may explain disease, guide treatment or inform preventive care. However, sequencing cannot be used to detect all types of variants: sometimes other types of genetic testing are required. |
| Genomic testing | A laboratory process used to analyse part or all of a person’s genome to support diagnosis, prognosis, monitoring or treatment of a condition. It involves the collection of a biological specimen and the extraction of DNA, sequencing, analysis, interpretation and reporting. |
| Genomics | The comprehensive study of the DNA of an organism (up to the entire genome), including how genes interact with each other and with the environment. |
| Genotype | The pair of alleles that an individual has at a given location in the genome. Where a person only has one copy of the gene (e.g. X-linked genes in males), their genotype is the one allele at that location. |
| Germline |
Germline cells are in reproductive tissues (eggs in the ovaries or sperm in the testes) and can transmit genetic information including variants to the next generation. When a person inherits a germline genetic variant it will normally be present in all cells of their body. Germline variant classifications: Assessment of the variant for pathogenicity, with five classes:
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| Heterozygous | When an individual’s two alleles for a given location in the genome are different. An individual who is heterozygous is called a heterozygote. |
| Homozygous | When an individual’s two alleles for a given location in the genome are the same. An individual who is homozygous is called a homozygote. |
| Horizon scanning | A systematic process to identify emerging trends, technologies, and other developments that could impact an organisation, industry, or specific area of interest. It can be used to prepare for future challenges, take advantage of new opportunities, and reduce risks. |
| Immunotherapies | Treatments that help a person's immune system fight disease, especially cancer. They work by boosting the immune system to more effectively target and attack harmful cells. |
| Monogenic condition | A condition that is caused by genetic variants within only one gene. For example, cystic fibrosis is caused by variants in the CFTR gene. |
| Non-coding regions | The parts of the genome that cannot be used to make an RNA template for a protein. Instead, they may control how or when a protein is made, help control other processes or they may have no known function. Non-coding regions make up about 99% of the human genome. |
| Nucleotide | A small building block that makes up DNA and RNA, also called a ‘base’. The nucleotides in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T). In RNA, the base uracil (U) replaces thymine. |
| Omics | Omics describes the comprehensive study of one type of biological molecule. For example, genomics (DNA molecules), transcriptomics (RNA molecules) and proteomics (proteins). |
| Penetrance | Penetrance describes how likely it is that someone with a disease-causing genotype will go on to develop the condition (phenotype). Some variants have full penetrance (i.e. all people with a disease-causing genotype are affected), while others have variable penetrance (i.e. some people with a disease-causing genotype will show signs and symptoms, whereas others may never show features of the condition). Understanding penetrance is an important consideration for genetic screening tests and for counselling patients about risk. See also Variable expressivity. |
| Person- and family-centred | An approach to health care that prioritises the preferences, needs and values of patients, and where appropriate their families, and actively involves them in decisions about their care. |
| Pharmacogenomics | The study of how a person’s genetic variants, including the variants present in their cancer, may affect the way they respond to medicines. It can be used to tailor treatment to maximise effectiveness and reduce side effects. |
| Polygenic condition | A condition that can be caused (or contributed to) by genetic variants within multiple genes. Polygenic conditions are also influenced by environmental factors, like lifestyle and diet. Common polygenic conditions include diabetes and heart disease. |
| Polygenic risk | A polygenic score is a statistical calculation of the combined effect of many small genetic changes that, together, increase or decrease the chance of developing a polygenic condition. Most polygenic scores were calculated by analysis of large datasets of people of European descent and may not be as effective predictors of disease in other ancestral groups. |
| Population-based screening | When everyone in a target group is offered a test to assess whether they may have a disease or are at increased risk of developing a disease before they have any signs or symptoms. The goal of population-based screening is to enable early detection and intervention, reducing the severity, incidence, and/or mortality associated with the disease. |
| Precision medicine | An approach to health care that can tailor prevention, diagnosis and treatment based on a person’s genomic, environmental and lifestyle information. |
| Predisposition | A genetic predisposition is an inherited genetic risk that may make individuals or families more likely to develop a particular condition. The type or level of risk varies greatly depending on the genetic variant and condition involved, and other lifestyle and environmental factors. |
| Protein | A molecule made using the instructions in genes. Proteins carry out most of the body’s functions. |
| Rare diseases | Health conditions that affect less than 1 in 2,000 people in Australia, and which are often serious and progressive. Most rare diseases have a genetic basis. |
| Re-analysis | When a person has a genomic test, the analysis looks at variants or genes that are known to be associated with the signs and symptoms they are experiencing. If no variant is found that might explain their signs and symptoms, the genomic data may be stored for re-analysis later. As researchers discover new gene:disease relationships, or the person develops new signs or symptoms, re-analysis can be used to look again at a person’s existing genomic data, checking genes or variants that were not looked at previously. |
| Recessive | A pattern of inheritance of a genetic trait. If an allele is recessive, then a person needs to have a disease-causing allele for both their copies of that gene to have the associated trait or condition. A person with only one copy of a recessive disease-causing allele will usually not have the condition and is called a carrier. |
| Reproductive carrier testing | Genomic screening offered to people planning pregnancy or early in pregnancy, to see if the person and their reproductive partner are at increased risk of having a child with a condition. If both people in the couple are carriers for a recessive condition then they have a 1 in 4 chance of having a child with that condition even though neither of the parents have it. |
| RNA (Ribonucleic acid) | A type of molecule important for gene expression that is made using DNA instructions (transcription). RNA can be a template to make proteins (translation) or it can have a role in other processes. RNA is similar to DNA in that it is also a molecule made up of a sequence of nucleotides connected in a row, although RNA has different types of nucleotides in its alphabet compared to DNA, and is often single-stranded. |
| Sequencing | A laboratory technique to determine the order of DNA nucleotide bases to understand genes or gene expression. Sequencing can look at only the coding regions (exome sequencing), the whole genome (genome sequencing) or all the RNA (transcriptome sequencing). |
| Singleton testing | When a person’s sample is analysed without also including their parents’ samples in the analysis. Many tests are done as singleton tests. |
| Somatic |
Somatic cells are the non-reproductive cells of all other organs that cannot transmit genetic information (including variants) to the next generation. Somatic variants are acquired during a person’s life. They are not inherited or passed on to children, but are relevant to many conditions such as cancer and vascular malformations.
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| Somatic vs germline variants | Somatic variants occur in non-reproductive cells and are acquired during a person’s life. They are not inherited or passed on to children, but are relevant to many conditions such as cancer and vascular malformations. Germline variants are variants that are present in germline cells. Germline variants can be inherited through egg or sperm cells, are normally present in every cell of the body and can be passed on to children. Both types have clinical importance, but the pattern of disease associated with germline gene variants is often different to the somatic variant occurring in the same gene. Germline and somatic analysis requires different genomic testing and management approaches. |
| Transcriptome | The complete set of RNA templates, transcribed as part of gene expression within an organism’s cell. |
| Trio testing | When a person’s sample is analysed along with their parents’ samples. Trio testing is particularly useful in genomics because everyone has millions of variants in their genome, most of which do not cause disease. Trio testing can help the analysis to more easily narrow down which of the genetic variants in the patient could be causing their condition. Quad testing is when a sample from a sibling is also included in the analysis. |
| Tumour agnostic therapies | Cancer treatments that target specific changes in cancer cells, irrespective of the tissue in which the cancer started in the body. Instead of focusing on the cancer’s location (like lung or breast), these therapies work by identifying and treating the genetic markers that drive cancer growth. |
| Ultra-rare diseases | Health conditions that affect less than 1 in 50,000 people in Australia, and which are often serious and progressive. Most ultra-rare diseases have a genetic basis. |
| Variable expressivity | A difference in the severity of a genetic condition among people with the same genotype. In some conditions, people with the same genotype can have a different level of severity of the condition or different signs or symptoms. Variable expressivity can mean it is impossible to predict exactly how a specific individual will be affected by a genetic condition, even if they have the same genetic variants as a family member. Understanding expressivity is important for counselling patients about risk. |
| Variant | A difference in a person’s DNA sequence compared to a reference sequence. Variants can be harmless, beneficial or linked to disease. Variants can be inherited by the next generation if they are present in germline cells, but cannot be passed on if they are only present in other cells of the body (somatic cells). There are many different types of genetic variant, and they can range in size from a single nucleotide variant (or single nucleotide ‘polymorphisms’, SNPs) to whole chromosomes. |