Genetic drift occurs. Medical search. Frequent questions

In small populations, fixation can occur in just a few generations. (wikipedia.org)
Drift increases the amount of genetic differentiation among populations if no gene flow occurs among them. (rwmansiononpeachtree.com)
In a species whose populations in the eastern Mediterranean basin have been substantially declined due to recurring mass mortality incidents and intensive harvesting, these markers are expected to assist studies of genetic structure and differentiation between populations. (researchgate.net)
Notably, we did not observe this haplotype in any of the African or Asian populations studied, suggesting that it may have been lost in these groups as a result of genetic drift. (discovermagazine.com)
The H2D haplotype has risen to frequencies of 10-25% in European populations with virtually no genetic variation, suggesting an extremely recent and rapid expansion of this haplotype. (discovermagazine.com)
Similarly the genetic variation within Saami and non-Saami populations in Scandinavia is dwarfing any difference between them. (upenn.edu)
The Faroe Islands are among the most isolated populations in the North Atlantic, and their low genetic diversity and small effective population size may have led to substantial genetic drift and loss of genetic diversity, and an enrichment of some pathogenic variants and complete loss of others. (nature.com)
Migration is a powerful force acting against genetic divergence among sub-populations (Hartl & Clark, Principles of Population Genetics, pp. 295-309). (blogspot.com)
All populations showed high global spatial genetic structure (SGS) and population differentiation. (researchsquare.com)
The high SGS of T. recurvata indicated low connectivity between urban populations, with strong evidence to suggest that this was the result of small population size and genetic drift. (researchsquare.com)
However, salmon hatcheries are a source of considerable controversy within the State of Alaska, primarily due to potential risks to wild stocks related to competition in the ocean and deleterious genetic 1 effects on wild populations when hatchery fish stray into natural spawning habitat. (uaf.edu)
1985) that addresses both the potential risks to wild stocks in terms of genetic diversity and population genetic structure as well as potential genetic risks to hatchery populations, and provides recommendations for how to minimize both. (uaf.edu)
We now have the genetic tools necessary to evaluate these principles empirically, allowing us to advance genetics policy for hatchery management in Alaska out of the theoretical realm, with more realistic context based on data from real salmon populations. (uaf.edu)
Outbreeding depression is identified in the Genetic Policy as a potential risk of hatchery programs to wild salmon populations. (uaf.edu)
The policy assumes first that wild populations are locally adapted, and second, that hatchery populations are likely to diverge from source wild populations through random genetic changes ('drift') as well as through adaptation to the hatchery environment. (uaf.edu)
We investigated whether CNVs constitute a common mechanism of genetic change during adaptation in experimental Caenorhabditis elegans populations. (biomedcentral.com)
In this study, we seek to determine if gene copy-number changes are a common class of genetic change during adaptation and what role, if any, natural selection plays in the maintenance and frequency increase of copy-number variants (CNVs henceforth) in experimental populations. (biomedcentral.com)
This can occur through gene flow, which is the transfer of genetic material from transgenic organisms to wild populations. (tutorialspoint.com)
In the face of environmental changes or the emergence of new pathogens, populations with high genetic diversity are more likely to have individuals with genetic traits that provide resistance or tolerance. (realdetroitweekly.com)
Speciation occurs when a single population becomes two separate, genetically non-identical populations that are unable to interbreed due to changes that produce physical, biological or behavioural barriers. (atarsurvivalguide.com)
The populations on either side may become different due to the process of natural selection, or they may become different due to mutation/genetic drift. (atarsurvivalguide.com)
The populations become so different that members of the different populations can no longer interbreed with one another to produce fertile offspring, and hence, speciation has occurred (leading to the creation of new species). (atarsurvivalguide.com)
The São Miguel do Oeste and Chapecó populations had similar frequencies of Val and Ile and were not in Hardy-Weinberg equilibrium, suggesting that a selection pressure or other evolutionary force has occurred. (geneticsmr.com)
Misconceptions about the use of genetic tests in populations. (who.int)

In 1968, population geneticist Motoo Kimura rekindled the debate with his neutral theory of molecular evolution, which claims that most instances where a genetic change spreads across a population (although not necessarily changes in phenotypes) are caused by genetic drift acting on neutral mutations. (wikipedia.org)
Drift consists of small changes (or mutations) in the genes of influenza viruses that can lead to changes in the surface proteins of the virus, HA (hemagglutinin) and NA (neuraminidase). (cdc.gov)
Genetic disorders result from new or inherited gene mutations . (amboss.com)
Certain genetic mutations or variations can increase the likelihood of developing specific conditions. (realdetroitweekly.com)
The latter occurs because of one or a series of mutations, and is known as "knockdown resistance" (kdr). (geneticsmr.com)
Antigenic drift involves small mutations in the genes of influenza viruses that lead to changes in HA and NA that accumulate over time, resulting in the emergence of novel strains that the human immune system may not recognize. (cdc.gov)

Every 10 to 15 years, influenza undergoes a dramatic genetic change ( antigenic shift ) which as described, is responsible for epidemics/pandemics. (science20.com)
While flu viruses evolve genetically all the time and often undergo antigenic drift, antigenic shift happens infrequently. (cdc.gov)
Changes in influenza viruses can take the form of antigenic drift or antigenic shift. (cdc.gov)

Strains of Nipah virus isolated from affected persons in Bangladesh have substantial genetic diversity ( 17 ). (cdc.gov)
The repeated out- breaks in Bangladesh and the genetic diversity of Nipah virus isolated from affected persons in Bangladesh suggest substantial diversity of the virus in the wildlife reservoir and repeated spillover of the virus from its reservoir to the human population. (cdc.gov)
The bottleneck limits the genetic diversity of. (rwmansiononpeachtree.com)
Is random genetic drift unimportant for generating morphological and physiological diversity among organisms? (blogspot.com)
Genome-wide SNPs provide researchers with precise estimates of population genetic diversity and structure and can be used to identify candidate adaptive loci. (edu.au)
Although genetic diversity within stands of trees is known to have community-level consequences, whether such effects are present at an even finer genetic scale is unknown. (mdpi.com)
We examined the hypothesis that genetic variability (heterozygosity) within an individual plant would affect its dependent community, which adds a new dimension to the importance of genetic diversity. (mdpi.com)
This shuffling and recombination of genetic information contribute to the genetic diversity observed in offspring. (realdetroitweekly.com)
Genetic diversity plays a vital role in evolution by promoting adaptability within a population. (realdetroitweekly.com)
Genetic diversity acts as a buffer against environmental challenges and diseases. (realdetroitweekly.com)
Genetic diversity provides the raw material for natural selection to operate. (realdetroitweekly.com)
RESULTS: To identify genetic factors linked to panicle architecture diversity in the two species, we used a set of 60 Chromosome Segment Substitution Lines (CSSLs) issued from third generation backcross (BC3DH) and carrying genomic segments from O. glaberrima cv. (bvsalud.org)
GII.17 noroviruses are composed of distinct genetic clusters (I, II, IIIa, and IIIb) and have shown potential for replacing historically more prevalent GII.4 strains, but the serological basis for GII.17 antigenic diversity has not been studied in children. (cdc.gov)
Diversification requires processes that generate diversity (mutation, recombination) and processes that filter this diversity (drift, natural selection). (lu.se)

What is genetic drift bottleneck effect? (rwmansiononpeachtree.com)
The bottleneck effect is an extreme example of genetic drift that happens when the size of a population is severely reduced. (rwmansiononpeachtree.com)
A bottleneck effect is the term used to describe the loss of genetic variation that occurs after outside forces destroy most of a population. (rwmansiononpeachtree.com)
An example of a bottleneck Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. (rwmansiononpeachtree.com)
A bottleneck is a point of congestion in a production system (such as an assembly line or a computer network) that occurs when workloads arrive too quickly for the production process to handle. (rwmansiononpeachtree.com)
An example where the effect of genetic drift is magnified is the so-called bottleneck effect. (rwmansiononpeachtree.com)
A genetic bottleneck occurs when a population is greatly reduced in size. (rwmansiononpeachtree.com)
What is genetic bottleneck in biology? (rwmansiononpeachtree.com)
Scientists believe cheetahs have already survived at least two genetic bottleneck events. (rwmansiononpeachtree.com)
When an event causes a drastic decrease in a population, it can cause a type of genetic drift called a bottleneck effect. (rwmansiononpeachtree.com)
When a threatened mammal species experiences inbreeding depression, genetic drift or a genetic bottleneck, their risk of extinction increases. (edu.au)

Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. (wikipedia.org)

Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. (wikipedia.org)
This fluctuation is analogous to genetic drift - a change in the population's allele frequency resulting from a random variation in the distribution of alleles from one generation to the next. (wikipedia.org)
It seems to me that in some morphological characters a substantial part of genetic variation in nonadaptive. (blogspot.com)
Despite the controversy, there is minimal understanding of how well hatchery production protocols mimic natural mating strategies or impact the maintenance of genetic variation and individual fish size in hatchery broodstock. (uaf.edu)
We will explore how the incorporation (wild) or exclusion (hatchery) of jack males may affect the maintenance of population level genetic variation and the size of female offspring in hatchery broodstock. (uaf.edu)
There is variation present in a population which has occurred due to processes in meiosis, such as independent assortment, crossing over and random fertilisation, as well as things such as mutation, errors in meiosis, errors in DNA replication etc. (atarsurvivalguide.com)

In the process of substitution, a previously non-existent allele arises by mutation and undergoes fixation by spreading through the population by random genetic drift and/or positive selection. (blogspot.com)
Some evolution at the morphological level can be attributed to natural selection and some is due to random genetic drift. (blogspot.com)
natural selection and random genetic drift are both necessary to explain evolution at the morphological level. (blogspot.com)
Neutral Theory and random genetic drift are integral parts of evolutionary theory. (blogspot.com)

Yet even with such mechanisms in play, genetic mutation rates for complex organisms such as humans are dramatically lower than the frequency of change for a host of traits, from adjustments in metabolism to resistance to disease. (uncommondescent.com)
A representation of how natural selection occurs, from the appearance of a mutation to the change in a population. (visionlearning.com)
Understanding how virus genetic structure varies in space may yield insight into how these pathogens are adapted to and dispersed by different hosts or vectors, the relative importance of mutation, drift, or selection in generating genetic variability, and where and when epidemics or epizootics are most likely to occur. (bepress.com)
The most common mutation is the deletion of 6 nucleotides at position 2281 and their replacement with 7 others, which occurs most commonly in Ashkenazi Jews. (medscape.com)

According to textbook knowledge, it is precisely the "invention of sex" and the resulting mix of paternal and maternal genes that enlarge genetic variety, thus facilitating rapid adaptation to adverse environmental conditions. (dkfz.de)
Genes, languages and culture drift across the map at different paces and driven by different forces. (upenn.edu)
Genetic drift is a change in the frequency of a population's genes and alleles over time, often by founder effects (when a small group of individuals relocate) or bottlenecking (when a large population is decimated, leaving a smaller group to repopulate). (visionlearning.com)
Such a "shift" occurred in the spring of 2009, when an H1N1 virus with genes from viruses originating from North American swine, Eurasian swine, humans and birds emerged to infect people and quickly spread, causing a pandemic. (cdc.gov)
Ohno [ 1 ] theorized that newly duplicated genes were freed from the constraints of natural selection, implicating a dominant role of genetic drift in their early evolutionary dynamics. (biomedcentral.com)
This can be done through genetic engineering, which involves the insertion of specific genes or DNA sequences into an organism's genome. (tutorialspoint.com)
Genetics refers to the study of genes and heredity, while inheritance refers to the process by which genetic information is transferred from parents to offspring. (realdetroitweekly.com)
The inheritance of traits occurs through the transmission of genes from parents to their offspring. (realdetroitweekly.com)

Genetic drift can also cause a new population to be genetically distinct from its original population, which has led to the hypothesis that genetic drift plays a role in the evolution of new species. (rwmansiononpeachtree.com)
Without the forces of natural selection genetic drift sets in and the species risks evolving to a dead-end position. (activegarage.com)
The Marmorkrebs clone is a separate species (Procambarus virginalis), which, as genetic studies have shown, has split from the slough crayfish found in the Everglades (Procambarus fallax) some 30 years ago. (dkfz.de)
The species studied do not show any obvious differences in habitat preference, and some of them even occur sympatrically at certain sites. (bioone.org)
Evolution is the gradual genetic change of a species over time due to unequal reproduction among members. (visionlearning.com)
However, the connectivity and genetic structure of species that survive in these urban landscapes has received little attention, especially with regard to epiphytic plants. (researchsquare.com)
Another fascinating example of directional selection in a changing context is industrial melanism, which occurs when a species of melanic moth escapes predation due to environmental changes. (tutorialspoint.com)
Phylogenetic analyses revealed several kinds of evolutionary patterns that occurred during GPCR evolution including one-to-one orthologous relationships, species-specific gene expansion, and episodic duplication of the entire GPCR repertoire in certain species lineages. (springer.com)
Genetic drift and selective forces have shaped the individual structure of a given receptor gene but also of the species-specific receptor repertoire - a process that is still ongoing. (springer.com)
Which of the various species concepts distinguishes two species based on the degree of genetic exchange between their gene pools? (easynotecards.com)

Antigenic shifts are probably due to genetic recombination (an exchange of a gene segment) between influenza A viruses that affect humans and/or animals. (cdc.gov)
if immediate recombination does not occur, these can manifest as some type of molecular, cellular, or organic system alteration. (cdc.gov)

Humans continue to evolve due to a variety of evolutionary forces: natural selection, artificial selection, genetic drift, and via transhuman breakthroughs. (visionlearning.com)

The mechanisms of genetic drift can be illustrated with a simplified example. (wikipedia.org)
Epigenetic mechanisms basically regulate the interpretation of genetic information. (dkfz.de)
Genetic and molecular analyses are essential in understanding the mechanisms underlying transgenesis and in evaluating the potential risks and benefits associated with the use of transgenic organisms. (tutorialspoint.com)
Gene flow can occur through various mechanisms, such as seed dispersal, pollen drift, and animal migration. (tutorialspoint.com)
Additionally, studying genetics allows scientists to explore the inheritance patterns of traits and the mechanisms behind genetic diseases. (realdetroitweekly.com)
The two forms of speciation are sympatric speciation and allopatric speciation , and for these to occur, different isolating mechanisms take place. (atarsurvivalguide.com)
This may occur due to individuals feeding off of different things or choosing specific mates, and may occur due to the post- or pre-productive isolating mechanisms. (atarsurvivalguide.com)

When few copies of an allele exist, the effect of genetic drift is more notable, and when many copies exist, the effect is less notable. (wikipedia.org)

Genetic drift describes random fluctuations in the numbers of gene variants in a population. (rwmansiononpeachtree.com)
Epigenetic variants are often influenced by genetic variants. (dkfz.de)
Epilepsy occurs in individuals with missense variants in STX1A that are predicted to disturb the interaction of STX1A with STXBP1. (nature.com)
Utilizing samples from a birth cohort, we investigated antibody and B-cell responses to GII.17 cluster variants in confirmed GII.17 infections in young children as well as demonstrated that the distinct genetic clusters co-circulate. (cdc.gov)

Genetic drift can result in the loss of rare alleles, and can decrease the size of the gene pool. (rwmansiononpeachtree.com)
Genetic drift takes place when the occurrence of variant forms of a gene, called alleles, increases and decreases by chance over time. (rwmansiononpeachtree.com)
Genetic drift is the drifting of the frequency of an allele relative to that of the other alleles in a population over time as a result of a chance or random event. (rwmansiononpeachtree.com)
Drift causes fixation of alleles through the loss of alleles or genotypes. (rwmansiononpeachtree.com)
Genetic drift may result in the loss of some alleles (including beneficial ones) and the fixation, or rise to 100 %, percent frequency, of other alleles. (rwmansiononpeachtree.com)

At least four pandemics of influenza occurred in the 19th century, three in the 20th century, and one thus far in the 21st century. (cdc.gov)

The process of genetic drift can be illustrated using 20 marbles in a jar to represent 20 organisms in a population. (wikipedia.org)
Proponents of biological determinism, which is the claim that many organisms' traits are determined primarily by their genetic makeup, argued that evolution could explain social behaviors such as altruism and aggression. (asu.edu)
Transgenic organisms are living organisms whose genetic material has been artificially modified to introduce specific traits or characteristics. (tutorialspoint.com)
In transgenic organisms, genetic analysis is used to determine the presence and expression of the foreign DNA sequences that have been introduced into the genome. (tutorialspoint.com)

Unless the second jar contains exactly 10 red marbles and 10 blue marbles, a random shift has occurred in the allele frequencies. (wikipedia.org)
In other words, each of the 16 possible allele combinations is equally likely to occur, with probability 1/16. (wikipedia.org)
Genetic drift is change in allele frequencies in a population from generation to generation that occurs due to chance events. (rwmansiononpeachtree.com)
Basques are a cultural isolate, and, according to mainly allele frequencies of classical polymorphisms, also a genetic isolate. (upenn.edu)

Many of the arthropod-borne viruses (arboviruses) show extensive genetic variability and are widely distributed over large geographic areas. (bepress.com)

In between epidemics, minor influenza genetic changes occur (antigenic drift). (science20.com)
Antigenic drift, along with waning immunity, results in annual influenza epidemics, since the protection that remains from past exposures to similar viruses is incomplete. (cdc.gov)

The most common method of genetic analysis is polymerase chain reaction (PCR), which is used to amplify specific DNA sequences. (tutorialspoint.com)
[ 3 , 4 ] Laboratory-confirmed influenza (via nasopharyngeal swabs for culture, polymerase chain reaction, or both) occurred in 228 participants in the IIV3-HD group (1.4%) and 301 participants in the IIV3-SD group (1.9%), a relative efficacy of 24.2% (95% confidence interval [CI], 9.7 to 36.5). (medscape.com)

In addition to the DiaSorin assay reformulation, the CDC laboratory observed drifts in the serum 25(OH)D assay performance (as reflected in QC pool shifts in the mean, up or down, by up to 10%) over the period of NHANES 2003-2006. (cdc.gov)

The geographic barrier is actively preventing gene flow from occurring. (atarsurvivalguide.com)

I suppose the point is that the collocation of "typical" (visible or invisible genetic) traits with certain cultures and/or languages is a matter of course: Both have geographical distributions and some are bound to coincide at any time. (upenn.edu)
The Genetic Policy does not prescribe specific mating practices for hatcheries, but one charge of the policy is to avoid artificial selection for certain traits, either consciously or unconsciously. (uaf.edu)
It is important to approach this topic with sensitivity and an understanding of how genetic traits are passed down through generations. (realdetroitweekly.com)
When individuals have different genetic variations, they possess a wider range of traits and characteristics. (realdetroitweekly.com)

In the middle of the 20th century, vigorous debates occurred over the relative importance of natural selection versus neutral processes, including genetic drift. (wikipedia.org)
Researching and detecting these processes is crucial as it allows managers to initiate genetic rescue before it is too late. (edu.au)
The interactions between pathogens and their hosts involve complex and diverse processes at the genetic, biochemical, phenotypic, population, and community levels, while the distribution and abundance of microorganisms in nature and their microbial processes are affected by both biotic and abiotic factors that act at different scales. (nationalacademies.org)

2013 ). As such, low connectivity would be expected in urban landscapes, as well as high spatial genetic structure (SGS) (Chaves et al. (researchsquare.com)

This involves managing the hatchery population in ways that reduce genetic changes due to artificial selective forces and demographic effects. (uaf.edu)

Ronald Fisher, who explained natural selection using Mendelian genetics, held the view that genetic drift plays at most a minor role in evolution, and this remained the dominant view for several decades. (wikipedia.org)
Here, we scrutinized the impact that the number and variety of the Rap-Phr family of regulators and cell-cell communication modules of B. subtilis has on genetic adaptation and evolution. (nature.com)
Intermarriage in the geographical zones close to the present-day Basque country must have occurred: for instance in Gascogne, previously written Guascogne, from the evolution of the Latin name Vasconia, where the root vasc- ([wask]) correspond to present-day "Basque" (which is a French spelling for a Spanish-influenced pronunciation). (upenn.edu)
1. Do you agree or disagree with the view expressed by Motoo Kimura that natural selection is necessary to explain evolution occurring at the morphological level? (blogspot.com)

7. In a eukaryotic cell, protein synthesis occurs in the A. nuclear envelope. (nursingdons.com)

Avian influenza viruses replicate in the gastrointestinal tract while human influenza viruses replicate in the respiratory tract-as conveyed by their differential genetic makeup. (science20.com)
The small genetic changes that occur in influenza viruses over time usually produce viruses that are closely related to one another, which can be illustrated by their location close together on a phylogenetic tree . (cdc.gov)

On the basis of sequence at the duplication loci, we estimate that the H2-specific duplication event occurred approximately 1.3 million years ago. (discovermagazine.com)
We designed seven novel microsatellite markers and used four cross-amplified loci to determine the basic genetic structure of T. recurvata . (researchsquare.com)

Indices of genetic isolation are calculated to indicate the likelihood of genetic drift occurring at any point during the period studied. (dur.ac.uk)
Genetic isolation can occur either prior to or following physical isolation, however in both cases, once isolation has occurred, the two groups acquire different phenotypes. (atarsurvivalguide.com)
Allopatric speciation is speciation that occurs due to geographic isolation . (atarsurvivalguide.com)

Outbreeding depression would occur if divergent hatchery fish stray onto wild spawning grounds, successfully interbreed, and alter the genetic composition of the next wild generation, thereby reducing the wild population's average survival and reproductive success. (uaf.edu)

Hypothetically, the period of rapid cell growth that occurs during adolescence could increase susceptibility to carcinogens, but little data exist to support or refute this. (cdc.gov)
2006) it would be good if that future epidemiological studies of relationships between lead exposures and cancer should include evaluation of genetic susceptibility factors, such as the ALAD gene. (who.int)

Interestingly, note that as our understanding of the molecular basis of genetic hearing loss increases, so does our understanding of the molecular basis of hearing itself, although it remains still largely unsolved. (medscape.com)

Overcoming all of these hurdles means there must be a corresponding change in the virion's genetic makeup. (science20.com)
Genetic drift is usually considered as a random change in the gene of a group population which has intense effects on the larger population in the future. (rwmansiononpeachtree.com)
One way flu viruses change is called "antigenic drift. (cdc.gov)
Type A viruses undergo both antigenic drift and shift and are the only flu viruses known to cause pandemics, while flu type B viruses change only by the more gradual process of antigenic drift. (cdc.gov)
Is the residence time of a pathogen sufficient to allow genetic exchange or change to occur? (nationalacademies.org)

The second infection occurred in May 2022 in a child who visited a wet market where live poultry were present [ 6 ]. (cdc.gov)

Each human cell contains 23 pairs of homologous chromosomes (corresponding in structure and genetic information, i.e., 23 chromosomes are inherited from each parent). (amboss.com)
During meiosis, the chromosomes pair up, exchange segments of genetic material, and then separate. (realdetroitweekly.com)

However, genetic drift can occur, resulting in natural hybrids. (gardeningknowhow.com)

This requires a combination of genetic, molecular, and ecological analyses. (tutorialspoint.com)
This means that offspring inherit a combination of genetic material from both parents. (realdetroitweekly.com)

Genetic analysis involves the study of an organism's genetic material, including its DNA, RNA, and proteins. (tutorialspoint.com)

The extent to which a person's immune protection is reduced against an antigenically drifted flu virus can vary, in part because different people may have different levels of pre-existing immunity against that flu virus. (cdc.gov)

Genetics and inheritance play a vital role in understanding the occurrence of genetic disorders and diseases. (realdetroitweekly.com)

One way to reduce the probability of outbreeding depression is to minimize the degree to which the genetic composition of the hatchery population is changed by hatchery practices. (uaf.edu)

however, H3N8 viruses of a different genetic lineage have been detected in U.S. wild birds and some mammals in the past. (cdc.gov)

Antigenic drift can sometimes result in a person becoming susceptible to flu virus infection again, as antigenic drift has changed the virus' antigenic properties enough that a person's existing antibodies won't effectively recognize and neutralize the antigenically different flu viruses. (cdc.gov)
Influenza infection occurs as an annual seasonal epidemic in winter or early spring in countries with temperate climates. (who.int)
According to a statement from the Guangdong Provincial Center for Disease Control and Prevention , the third human infection with H3N8 virus occurred in an adult in China who reportedly had a history of exposure to live poultry and wild birds (which had been observed around the home). (cdc.gov)

They also have an age structure and genetic fitness. (explorable.com)
and to 3) discuss how urbanisation can affect genetic structure in epiphytes. (researchsquare.com)

Antigenic drift is also a primary reason why the composition of flu vaccines for use in the Northern and Southern Hemispheres is reviewed annually and updated as needed to keep up with evolving flu viruses. (cdc.gov)
Antigenic drift is the primary reason people can get influenza more than once and why it is necessary to annually review and update the composition of influenza vaccines. (cdc.gov)

These are regulated by small chemical tags attached to DNA, the genetic substance. (dkfz.de)

Microbes commonly display great genetic plasticity, which has allowed them to colonize all ecological niches on Earth. (nature.com)

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