Show When a virus replicates or makes copies of itself, it sometimes changes a little bit. These changes are called “mutations.” A virus with one or several new mutations is referred to as a “variant” of the original virus. The more viruses circulate, the more they may change. These changes can occasionally result in a virus variant that is better adapted to its environment compared to the original virus. This process of changing and selection of successful variants is called “virus evolution.” Some mutations can lead to changes in a virus’s characteristics, such
as altered transmission (for example, it may spread more easily) or severity (for example, it may cause more severe disease). Some viruses change quickly and others more slowly. SARS-CoV-2, the virus which causes COVID-19, tends to change more slowly than others such as HIV or influenza viruses. This could in part be explained by the virus’s internal “proofreading mechanism” which can correct “mistakes” when it makes copies of itself. Scientists continue to study this mechanism to better understand how it works. It is normal for viruses to change, but it is still something scientists follow closely because there can be important implications. All viruses, including SARS-CoV-2, the virus that causes COVID-19, change over time. So far hundreds of variations of this virus have been identified worldwide. WHO and partners have been following them closely since January 2020. Most changes have little to no impact on the virus’ properties. However, depending on where the changes are located in the virus’s genetic material, they may affect the virus’s properties, such as transmission (for example, it may spread more easily) or severity (for example, it may cause more severe disease). WHO and its international network of experts, are monitoring changes to the virus so that if significant mutations are identified, WHO can report any modifications to interventions needed by countries and individuals to prevent the spread of that variant. The current strategies and measures recommended by WHO continue to work against virus variants identified since the start of the pandemic. See WHO’s Disease Outbreak News for reports on variants. The best way to limit and suppress the transmission of COVID-19 is for people to continue taking the necessary precautions to keep themselves and others safe. Since the start of the outbreak, WHO has been working with a global network of expert laboratories around the world to support testing and better understanding of SARS-CoV-2, the virus that causes COVID-19. Research groups have sequenced SARS-CoV-2 and shared these on public databases, including GISAID. This global collaboration allows scientists to better track the virus and how it is changing. WHO’s global SARS-CoV-2 laboratory network includes a dedicated SARS-CoV-2 Virus Evolution Working Group, which aims to detect new mutations quickly and assess their possible impact. WHO recommends that all countries increase the sequencing of SARS-CoV-2 viruses where possible and share sequence data internationally to help one another monitor and respond to the evolving pandemic. SARS-CoV-2 spreads primarily through human-to-human transmission, but there is evidence of transmission between humans and animals. Several animals like mink, dogs, domestic cats, lions, tigers and raccoon dogs have tested positive for SARS-CoV-2 after contact with infected humans. There have been reports of
large animal outbreaks in mink farms in several countries. SARS-CoV-2 can change while infecting minks. It has been observed that these mink variants are able to transmit back into humans through close contact with the mink. Preliminary results suggest that the mink variants infecting humans appear to have the same properties as other variants of the SARS-CoV-2 virus. Further research is needed to better understand whether these mink variants will cause sustained transmission among
humans and could have a negative impact on countermeasures, such as vaccines. See WHO’s Disease Outbreak News on Denmark ( 3 December 2020) WHO works closely with other organizations, such as the Food and Agriculture Organization of the United Nations, and the World Organisation for Animal Health, to evaluate situations of SARS-CoV-2 in animals and transmission occurring between animals and humans. Assembly DNA sequencing technology cannot read whole genomes in one go; instead it reads short pieces of bases from a genomic sequence. Sequence assembly is aligning and merging fragments from a longer DNA sequence to reconstruct the original sequence. Bioinformatics The science of analysing genomic data. Candidate genes Genes of interest related to phenotypes or disease states. Clinical geneticist This is a medical doctor with special training in genetics who meets with patients to evaluate, diagnose and manage genetic disorders. Clinical geneticists also assist in the management of genetic diseases by identifying preventable complications through early and accurate diagnosis and surveillance. CRISPR-Cas9 CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats) is a method of genetic manipulation consisting of two key molecules that introduce a change into the DNA. The molecules are:
Involves new forms of sequencers that can read long distances down one strand of DNA. There are currently two effective technologies:
This is the study of how genomic variation within the individual or their disease (including gene expression, epigenetics, germline and somatic mutations) influences one person’s response to drugs. The aim is to optimise drug therapy by maximising therapeutic effect and minimising adverse effects. Pipeline A process for the preparation, development, production and analysis of genomic data. Population genomics The large-scale application of genomic information to study populations, including entire genomes of an entire species (e.g., kākāpō). Prokaryote Unicellular microbial organism that lacks a nucleus. All bacteria are prokaryotes. A related group are Archaea – these are also unicellar but are different to bacteria. Proteomics RNA (made from turned-on genes) is translated into protein. Proteomics is a technique to look at the broad range of proteins in a cell or tissue (using mass spectrometry). We can usually identify which proteins are present in a cell and what they are doing. RNA RNA (ribonucleic acid) is the molecule that takes information from DNA to make protein and has many other activities. RNA is only made from genes in the DNA that are turned on. Short read sequencing (also known as next generation or second generation sequencing) Small segments of DNA strands put in order then assembled in the genome. This is assembled by looking at the sequence of each chunk and finding sequences that overlap (aligning). SNPs About 90 percent of human genome variation can be accounted for by single nucleotide polymorphisms, or SNPs (pronounced "snips"). These are variations that involve just one nucleotide, or base. Somatic Refers to the cells of the body in contrast to the cells that make sperm or eggs. Structural variation or Structural Variants (SVs) Structural variation describes individual or group differences in genome structure, such as gene deletions, insertions, duplications, inversions, and translocations. These variant regions are scattered throughout genomes and are often associated with gene expression changes and observable differences among individuals (phenotypic differences). Transcriptomics Sequencing RNA from a tissue or cell to measure the set of active genes. Variome The whole set of genetic variations found in populations of species. Whole genome sequencing (WGS) The process of determining the complete DNA sequence of an organism's genome.What is a variant of a gene called?Gene variants (also known as mutations) can have varying effects on health, depending on where they occur and whether they alter the function of essential proteins.
What is it called when the structure of genes changes?A mutation is a change in a genetic sequence. Mutations include changes as small as the substitution of a single DNA building block, or nucleotide base, with another nucleotide base.
What causes change in gene structure?Gene flow, natural selection and genetic drift are processes that play a major role in shaping the genetic structure of natural populations.
What is called mutation?A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection.
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The changing of the structure of a gene resulting in a variant form that may be transmitted
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