Genetic Drift – Difference Between Genetic Drift And Genetic Flow.


Genetic Drift – Difference Between Genetic Drift And Genetic Flow.

Genetic drift, a key concept in evolutionary biology, pertains to the unpredictable fluctuations in allele frequencies within a population as time progresses.

It could be difficult to understand in that manner. I will simplify the term for better clarity.

You can think of it like a jar filled with marbles of different colours, each representing a different trait or gene in a population. If you randomly pick out a few marbles and remove them from the jar, the ones left behind would represent the new population.

The traits or genes that were removed may no longer be present in the population, or they might become more common if they happened to be selected more often.

Likewise, unpredictable occurrences like natural disasters, disease outbreaks, or migration can influence the prevalence of specific traits or genes within a population. As time progresses, these chance events can result in alterations to the population’s genetic composition. This phenomenon is known as genetic drift.

It is important to note that genetic drift differs from natural selection, which happens when certain traits or genes offer individuals advantages, leading to improved survival and reproduction. In contrast, genetic drift is a random process that does not necessarily lead to any specific outcome.


Genetic drift, sometimes called allelic drift or the Wright effect occurs when the frequency of a particular gene variant or allele in a population changes randomly. This process can sometimes lead to the complete disappearance of certain gene variants, reducing the population’s genetic diversity.

Alternatively, it can result in rare alleles becoming much more common and even the only allele present in the population.

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History Of Generic Drift:

The notion of genetic drift was initially introduced by Sewall Wright, an American geneticist, during the early 20th century. Wright’s research focused on investigating the consequences of inbreeding in small populations.

During his studies, he recognized that chance events, such as the death of individuals or the failure of specific alleles to be transmitted to subsequent generations, could lead to random fluctuations in allele frequencies.

Wright coined the term “drift” to describe this phenomenon and proposed that it played a substantial role in shaping the genetic composition of small populations.

Building upon Wright’s work, Motoo Kimura, a geneticist, further expanded on the concept of genetic drift in the 1950s and 1960s. Kimura developed mathematical models to elucidate the effects of genetic drift on allele frequencies.

His research demonstrated that genetic drift could significantly influence the evolution of populations, particularly those that were small and geographically isolated from other populations.

Genetic drift is widely accepted as an important evolutionary mechanism alongside natural selection, mutation, and gene flow. It holds particular importance in small populations, where chance events can profoundly impact the population’s genetic structure over time.

Types Of Genetic Drift:

Genetic drift can be categorized into two primary forms: bottleneck events, which happen when a population experiences a sudden and severe decline and is subsequently repopulated by a small group of survivors, and Founder effects, which occur when a new population is initiated by only a few individuals from the original population.

Population bottleneck:

Genetic drift (article) | Natural selection | Khan Academy
An instance of the bottleneck effect is when a natural calamity strikes a population, causing only a few individuals to survive. The genetic drift resulting from this event will impact the surviving population for numerous generations, as per Clark from Openstax.- Credit: Biologyonline.

The bottleneck effect occurs when a population experiences a significant reduction in its size due to a natural disaster. This event can lead to the genetic distribution among the population being affected by genetic drift, which becomes more pronounced. As a result, the genetic variation in the population decreases since fewer individuals are available for mating.

When the rate of genetic drift intensifies within a population, it results in the disappearance or fixation of certain alleles. A reduction in the effective genetic size characterizes this occurrence.

Although populations that undergo a bottleneck event may eventually reproduce and grow in size once more, the genetic diversity among these populations declines at a rate proportional to the magnitude of the catastrophe until new individuals are introduced through migration or new mutations arise.

The impact of a bottleneck event on a population’s genetic variation is influenced by its scale and duration, which are assessed through mathematical calculations to determine their significance.

Founder Effect:

Founder effect - Wikipedia
The genetic makeup of the new colony may not fully represent the original population due to the isolation of the new colony from the original population.

In biology, the founder effect is described as forming a small population due to a small number of individuals leaving their original population to establish a new colony. This new population may not have the same genetic makeup as the original population, leading to significant genetic drift within the small population.

This phenomenon is often observed in fungi species, where spores disperse and establish new colonies in different environments, resulting in colonies with different alleles than the original population.

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Genetic Drift In Evolution

Genetic drift alters the frequency of specific alleles within populations, leading to their increase or decrease. In normal populations, the effects of genetic drift tend to balance out over the long term.

However, if the frequency of an allele reaches zero, the impact of genetic drift cannot be nullified unless a new mutation generates that allele again. Genetic drift holds significance in the process of evolution as it determines the destiny of a mutation, dictating whether it will vanish or become permanently established within a population after a few generations.

Genetic drift remains significant even for commonly occurring genes, particularly in non-ideal populations characterized by small sizes.

Regularly, if an allele becomes fixed within a generation, it will likely increase in subsequent generations. However, in the context of genetic drift, what happens in one generation does not necessarily follow the same pattern in the generations that follow.

Therefore, if an allele increases in one generation, it may either increase or decrease in the subsequent generations.

The adaptation of a subdivided population involves two distinct phases. The first phase is characterized by genetic drift, where certain alleles’ random loss or fixation occurs by chance. This process allows the population to explore new genetic variations. The second phase involves the natural selection of the most advantageous genes that emerged during the first phase.

These genes are then transferred to other populations through migration. The genetic drift theory plays a significant role in the evolutionary process of individuals, as it maintains a delicate balance between mutations and gene drifting, contributing to the overall genetic variation.

Mutations introduce new alleles, while gene drifting can either eliminate or permanently establish these new alleles.

Difference Between Genetic Drift And Genetic Flow

Genetic drift and gene flow are distinct mechanisms that change populations’ genetic composition, albeit through different processes.

Genetic drift refers to the random variation in allele frequencies within a population, arising from chance occurrences like genetic mutations, genetic bottlenecks, or founder effects. It is more likely to manifest in small populations, where chance events can exert a more pronounced impact on the genetic profile.

Over time, genetic drift can lead to the reduction of genetic diversity or the fixation of specific alleles, thereby influencing the evolution of the population.

On the other hand, gene flow involves the transfer of genes between populations, facilitated by migration or other means. Gene flow introduces new genetic variations into a population, augmenting its genetic diversity.

Additionally, gene flow can counteract the effects of genetic drift by reintroducing alleles that may have been lost due to chance events. This gene exchange can occur between geographically proximate populations or through dispersal mechanisms like wind, water, or animal transportation.

To summarize, genetic drift entails random fluctuations in allele frequencies due to chance events, while gene flow encompasses the movement of genes between populations through migration or other mechanisms. Both mechanisms significantly affect populations’ genetic composition and species’ evolution.


In summary, upon analyzing and comprehending the notion of generic drift, we can deduce that it refers to when a term or concept gradually loses its initial meaning and becomes broader or less precise. Multiple factors, such as cultural shifts, technological advancements, and societal changes, influence this phenomenon.

General drift can significantly affect communication, leading to misunderstandings and confusion. To prevent generic drift, it is vital to remain cognizant of the evolving meanings of terms and concepts and adapt accordingly.

In general, comprehending generic drift is crucial for effective communication and ensuring the accurate transmission of messages.


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