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Genetic Diversity

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Genetic Diversity

Genetic diversity can be summed up by the total number of different alleles found within a species. These differences allow the species to adapt to their changing environments, ensuring their continuation. This process results in species that are better adapted to their environment and is known as natural selection.

Diversity begins with small differences in organisms’ DNA base sequence and these differences give rise to different traits. Random mutations or events occurring during meiosis cause these traits. We will take a look at the effects of these different traits and examples of genetic diversity.

Meiosis is a type of cell division.

Causes of genetic diversity

Genetic diversity stems from changes in the DNA base sequence of genes. These changes can occur due to mutations, which describe spontaneous changes to DNA and meiotic events, including crossing over and independent segregation. Crossing over is the exchange of genetic material between chromosomes while independent segregation describes the random arrangement and separation of chromosomes. All of these events can give rise to different alleles and therefore contribute to genetic diversity.

Effects of genetic diversity

Genetic diversity is very important as it is the main driver of natural selection, the process in which organisms in a species that possess advantageous traits survive and reproduce. These advantageous traits (and also disadvantageous ones) arise from different variations of genes: these are called alleles.

The gene encoding a Drosophila’s wing length has two alleles, the ‘W’ allele gives rise to long wings whereas the ‘w’ allele gives rise to vestigial wings. Depending on which allele a Drosophila possesses determines their wing length. Drosophila with vestigial wings can’t fly and so they are less likely to survive compared to those with long wings. Alleles are responsible for anatomical changes, like Drosophila wing length, physiological changes, like the ability to produce venom, and behavioural changes, like the ability to migrate. Take a look at our article on Natural Selection, which explores the process in greater detail.

The greater the genetic diversity, the more alleles there are within the species. This means there is a greater chance for the continuation of the species as some organisms will possess traits that allow them to survive in their environment.

Low genetic diversity

Greater genetic diversity is advantageous for a species. What happens when there is low genetic diversity?

A species with low genetic diversity has few alleles. The species has, then, a small gene pool. A gene pool describes the different alleles present in a species and by having few alleles, the continuation of the species is at risk. This is because the organisms have a reduced probability of possessing traits that allow them to survive the changing environment. These species are highly vulnerable to environmental challenges, such as disease and temperature changes. As a consequence, they are in danger of becoming extinct. Factors such as natural disasters and excessive poaching could be the cause of this lack of genetic diversity.

An example of a species suffering from low genetic diversity is the Hawaiian monk seal. As a result of hunting, scientists have reported an alarming decline in seal numbers. Upon genetic analysis, scientists confirm low levels of genetic diversity in the species. They are categorised as endangered.

Examples of genetic diversity in humans

The ability of a species to adapt to environmental challenges and changes as a result of allelic diversity is remarkable. Here, we will take a look at examples of humans expressing genetic diversity and its effects.

Malaria is an endemic parasitic disease in sub-Saharan Africa. Scientists have discovered that the FY gene, which codes for a membrane protein that the malaria parasite needs to enter red blood cells has two alleles: the ‘wildtype’ alleles which code for the normal protein, and the mutated version which inhibits the protein function. Individuals possessing the mutated allele are resistant to malarial infection. Interestingly, this allele is only present in sub-Saharan Africa. This is a great example of how a certain subset of individuals possessing an advantageous allele increases their chances of survival in the face of environmental challenges.

Another remarkable example is skin pigmentation in response to ultraviolet (UV) radiation. Different regions of the world experience differences in UV intensities. Those found near the equator such as sub-Saharan Africa experience a higher intensity. The gene MC1R is involved in melanin production. Melanin production determines skin color: pheomelanin is associated with fair and light skin while eumelanin is associated with darker skin and protection against UV-induced DNA damage. The allele an individual possesses determines the amount of pheomelanin or eumelanin produced. Scientists have theorised that individuals inhabiting regions where UV radiation is higher possess the allele responsible for dark pigmentation to protect against DNA damage.

African genetic diversity

Studies have shown that African populations possess extraordinary levels of genetic diversity compared to non-African populations. How did this come to be?

To date, there are several hypotheses. However, evidence has shown that modern-day humans originated and evolved in Africa. Africa has undergone more evolution and experienced genetic diversity longer than any other present population. After migrating to Europe and Asia, these populations experienced dramatic reductions in their gene pools. This is because only smaller populations migrated. As a result, Africa remains remarkably diverse while the rest of the world is just a fraction.

The dramatic gene pool and population size reduction is called a genetic bottleneck. We can explain it with the ‘Out of Africa’ hypothesis. Don’t worry, you won't need to know this hypothesis in great detail but it is worth appreciating the origins of genetic diversity.

Genetic Diversity - Key takeaways

  • Genetic diversity describes the total number of different alleles found within a species. This diversity is primarily caused by random mutations and meiotic events, such as crossing over and independent segregation.
  • An advantageous allele in a human gene confers protection against malarial infection. In regions where UV intensity is high, individuals are more likely to possess alleles that grant them darker skin pigmentation. These examples reflect the benefits of genetic diversity.
  • Low genetic diversity puts species at risk of extinction. It also makes them vulnerable to environmental challenges.
  • The genetic diversity found in non-African populations reflects the diversity found originally in Africa.

Frequently Asked Questions about Genetic Diversity

Genetic diversity describes the number of different alleles present in a species. This is primarily caused by spontaneous mutations and meiotic events. 

Low genetic diversity describes a population possessing few alleles, reducing their chances of being able to survive and adapt. This puts these organisms at risk of extinction and makes them vulnerable to environmental challenges, such as disease. 

Genetic diversity is important as it is the driver of natural selection. Natural selection produces organisms that are best suited to the environment and its challenges. This process ensures the continuation of a species, and in this case, the continuation of humans. 

Crossing over is a meiotic event that involves the exchange of DNA between chromosomes. This increases genetic diversity as the resulting chromosomes are different from the parental chromosomes. 

African populations have experienced evolution longer than any other existing populations as scientists speculate that modern-day humans originated in Africa. The migration of smaller African populations to Europe and Asia means that these subsets reflect only a fraction of the diversity found in Africa. 

Final Genetic Diversity Quiz

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What is genetic diversity?

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Genetic diversity is the total number of alleles found within a species. 

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What are alleles?

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Alleles are different versions of the same gene.

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How are different alleles created?


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Different alleles are created by random mutations in DNA and meiotic events. 

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What process relies on genetic diversity?


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Natural selection. 

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Briefly describe natural selection. 


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Natural selection is the process in which organisms that possess advantageous alleles that enable them to endure environmental challenges survive and reproduce. 

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What are the consequences of low genetic diversity in a species?


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Low genetic diversity puts the species at risk of extinction as the organisms are vulnerable to environmental changes, such as disease. This is because a small gene pool reduces the chances of organisms possessing advantageous alleles. 

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Identify some factors that reduce genetic diversity. 


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Natural disasters. Excessive poaching. 

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What meiotic events increase genetic variation?


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Crossing over and independent segregation. 

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According to evidence, where did modern-day humans originate?


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Africa. 

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Why does Africa have the greatest level of genetic diversity?


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Evidence suggests that modern-day humans originated in Africa, which means that the continent has experienced evolution longer. Smaller populations migrated to Europe and Asia and these populations represent only a fraction of the genetic diversity found in Africa due to a genetic bottleneck.

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Describe the allele that confers malarial protection.


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An allele of the FY gene encodes a non-functional protein that inhibits the entrance of the parasite into red blood cells. Individuals possessing this alleles are resistant to malarial infection. 

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Describe the allele that confers protection against UV radiation. 


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The MCR1 gene is responsible for the amount of pheomelanin or eumelanin production. Pheomelanin grants fairer skin while eumelanin confers darker skin. Populations inhabiting regions with high UV exposure are more likely to possess the allele producing more eumelanin as darker pigments protect against DNA damage.  

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Describe crossing over. 


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Crossing over occurs in meiosis and describes the exchange of genetic material between chromosomes. This increases genetic diversity. 

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Describe independent assortment. 


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Independent assortment occurs in meiosis and describes the random arrangements and separation of chromosomes. This increases genetic diversity. 

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Identify some environmental challenges that species with low genetic diversity are vulnerable to. 


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Disease. Temperature changes. Natural disasters. 

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What is the importance of aseptic techniques?

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Aseptic techniques ensure that bacterial samples are not contaminated. They also ensure that pathogenic microorganisms do not grow. 

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Identify 4 examples of aseptic techniques. 

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Wash hands before handling agar plates. Disinfect workspaces with an antibacterial cleanser. Use a bunsen burner to flame wire hoops. Flame bottle necks of bacterial broth. 

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Why are bunsen burners used in aseptic techniques?


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Bunsen burners prevent the entry of microorganisms into your culture. 

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What piece of equipment is used to transfer bacteria into agar plates?


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Flamed wire hoops. 

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Identify the 4 stages of microbial growth. Under what conditions does the microbial growth curve occur?


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The lag phase, exponential (log) phase, stationary phase and death phase. This occurs in a closed system. 

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Describe the lag phase of microbial growth. 


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The lag phase involves a small number of bacteria adjusting to their environment. There is very little growth happening at this stage. 

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Describe the exponential phase of microbial growth. 


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The exponential phase involves the rapid increase of the bacterial population due to binary fission. The bacteria grow in optimal conditions. 

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Describe the exponential phase of microbial growth. 


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The exponential phase involves the rapid increase of the bacterial population due to binary fission. The bacteria grow in optimal conditions. 

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Describe the stationary phase of microbial growth. 


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The stationary phase involves the plateau of bacterial growth. At this stage, the rate of bacterial growth is equivalent to the rate of bacterial death. This is because of the accumulation of waste products and the depletion of nutrients. 

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Describe the death phase of microbial growth. 


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The death phase involves the toxic accumulation of waste products and the starvation of nutrients. The rate of bacterial death exceeds the rate of bacterial growth. 

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What is a zone of inhibition?


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A zone of inhibition describes the clear area around an antibiotic to indicate the killing of bacterial colonies. 

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How do you calculate the area of a zone of inhibition?


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Find the diameter first. Then use πd/4 to find the area. 

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What are antimicrobial substances?


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Antimicrobial substances inhibit the growth of bacteria and kill bacteria. 

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What do you observe on an agar plate that indicates the presence of bacteria?


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The presence of bacteria is indicated by cloudy-white areas on an agar plate.

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What does a small zone of inhibition indicate?


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A small zone of inhibition indicates that bacteria may be resistant to the antibiotic. 

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What does a large zone of inhibition indicate?


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A large zone of inhibitions indicates that bacteria are highly susceptible to the antibiotic.

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What does a large zone of inhibition indicate?


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A large zone of inhibitions indicates that bacteria are highly susceptible to the antibiotic.

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