Behavioural Genetics

8 Examples That Prove Behavior is Genetic

“Behavioral traits are complex, either learned or acquired by gene-environment interaction, most of the traits have a genetic foundation and fall under the second category.” 


The psychology, biology and genetic science behind behavior have been a hot topic for researchers for so many years. The psychological definition of behavior traits explains that genes govern traits while their interaction with the environment produces variability depending upon the requirement. 

While another definition in a layman explains, “Due to the interaction of environment and genetic traits various behavioral traits produce.” 

Functional, structural and biochemical traits are well studied in modern-day science. Put simply, traits are phenotypes and produced by a ‘definite genotype’. Genes make proteins, every type of protein, we know. 

This process is important for our survival on earth. But the question is can we study behavior traits by genetics? As we know, behavior is learned but also has a genetic background, studies suggest.  

This article makes sense in support: Is Behavior Genetic? Lets findout.

Biologists and psychologists have different views on the behavioral development of an organism. As per the psychological view, behaviors are developed by environmental interaction but as per biologists, they may be governed by some genetic traits as well.

However, both groups of scientists agree with the theory that behavioral characters are influenced by the inheritance of traits and their interaction with the environment.

But the question is what are those traits? And are well studied or not! let us go through some examples which prove that behavioral traits are genetic.

8 Examples That Prove Behavior is Genetic 

To make things more clear, we will see first some examples of animal models elaborative and then move to some human behavioral traits. 

1. Hygiene trait in honey bees:

The honey bee is the best model organism for studying behavior genetics. It has a specialized social arrangement with structured classification based on functionality. Each bee is categorized into Queen, Drones and workers. Each bee performs a different function even though its genetic composition is different as well. 

W. C. Rothenbuhler studied “hygiene” behavior in two species of honeybee. He picked bees from American foul-brood and Van Scoy.

A pair of recessive alleles govern the trait of hygiene. The hygiene trait is governed by a pair of recessive alleles. The worker bees from America’s foul-brood line maintain hygiene by removing dead pupae from their hive while the Van Scoy line bees are non-hygienic. It leaves the dead pupae in the compartment of hives.

Interestingly, when Rothenbuhler crosses both types of bees and observed results in F1 progeny, all the F1 progeny are non-hygienic. When drones from F1 lines are backcrossed with the queen of hygiene bees, four different types of progeny are observed in F2 progeny,

Behavioural Genetics
The image represents the behavior of hygiene and the opening of hives in the bee. u+ gene codes for hygiene-removes dead pupae, u- is for non-hygiene- not removing dead pupae, r+ for opening hives and r- for not opening hives.
  1. Pure hygienic bees
  2. Bees that did not open hive compartments but removed dead pupae (those hive compartments are opened by beekeepers).
  3. Bees that opened hive compartments but did not remove the dead pupae.
  4. Non-hygienic bees.   

The hygiene trait is controlled by two genes, one gene that controls the behavior of uncapping or opening hive compartments (called “r)  and another gene controls the trait of removal of pupae from the hive (called “u).

Interaction between these two genes produces various phenotypes in the F2 progeny. Conclusively, Rothenbuhler’s experiment explained that behavior traits have a genetic base and are controlled by separate genetic traits. 

2. The behavior of collecting Alfalfa pollen by honey bees:

Yet another example of ‘collecting alfalfa pollen’ by honey bees is controlled by genetic traits. 

Studies show that some bees collect a huge amount of alfalfa pollen while some collect less. Crossing between these two types of bees shows an intermediate tendency to collect alfalfa pollen, exactly after the 8th generation. 

The graphical representation is shown here,

Graphical representation of pollen collection behavior in two different populations of bees.

The preference for collecting alfalfa pollen follows the pattern of Mendelian inheritance which means, a specific genotype governs the trait of ‘collecting alfalfa pollen’. 

Notedly, theoretically, this specific behavior should be learned from parents but it’s inherited in a specific pattern. 

The present example is evidence that social skills and behavior (like the collection of alfalfa pollen) in bees are learned and show genetic inheritance as well. 

3. Searching for food in bees: 

Honey bees search for food in a definite pattern and travel in a specific diameter. Its complex behavior trait is learned as well as inherited. 

Italian bees have a slower dancing rhyme and travel 100 meters in search of food. While the Australian race of bees has fast dancing rhymes and can travel 80 meters in search of food. When the population of both types of bees mixed, show misunderstood behavior of rhyming and distance traveled. This change influences the morphological behavior of bees.

Their behavior after the crossing is explained in the image below.

Behavioural Genetics
The image represents the distance traveled by two different populations of bees, before mixing and after mixing the population.

Now if you understand behavior genetics and how it works, let’s take some human behavior examples.  

4. Atypical cat-like cry in the case of the cri-du-chat syndrome:

The cat-like cry is an uncommon and rare behavior reported in a special group of children. Though it’s a rare form of a genetic condition that occurs 1 in around 50,000 children worldwide, caused by a copy number variation mutation. 

In this condition, a part of chromosome 5 gets deleted during the fetal developmental cell division. The classic symptom of the present condition is a high-pitch & cat-like cry. 

Studies suggest that 5p deletion loses many vital genes required for various metabolic and psychological development. 

5. Mental and cognitive problems in ASD: 

ASD stands for Autism Spectrum Disorder, which is a developmental neurological disorder, involving behavioral, communication and cognitive problems. Notedly, other social issues are also reported in patients.

ASD is a proven genetic polygenic disorder that occurs by gene-environment interaction. Genome-wide association studies and whole-genome sequencing demonstrates that the condition is polygenic and doesn’t show any specific inheritance pattern. 

Studies also suggest that more than 50 various candidate genes are identified, having a definite role in the ASDs. Some of them are COMT, SETD1A, DPYD, ARC, and LAMA2 genes. 

Mutation, copy number variation or abnormal expression of candidate genes results in various degrees of autistic characteristics. The more the genes involved, the more serious the symptoms are!

Moreover, external environmental factors like exposure to radiation or high lead content also result in autistic conditions. Studies suggest that such factors may produce mutation within this group of genes. 

Conclusively, ASD is a proven genetic condition that originated from interaction with the environment. 

6. Definite role of MTHFR gene in psychiatric development: 

MTHFR stands for methylenetetrahydrofolate reductase is an enzyme encoded by a gene MTHFR located on chromosome 1. The enzyme is involved in folate metabolism thereby in DNA methylation. 

Mutation in the MTHFR gene causes abnormal DNA methylation (either under or overexpression). Studies suggest that MTHFR is involved in psychiatric development. 

Mutation in the MTHFR gene has involvement in various psychiatric disorders like depression, ADHD, bipolar disorder or schizophrenia. 

7. The polygenic base of bipolar disorders:

Scientific studies proved that genetics has been involved in 90% of bipolar disorders and are frequently inherited too. It is defined as, a sudden, rapid or extreme change in psychological behavior, mood and energy. 

Symptoms of conditions are frequently extreme and appear during early and late adulthood. At a genetic level DISC1, NRG1, TPH2, G72/DAOA and DAT1 are some of the common genes involved in the conditions. 

However, there are as many as 65 to 70 various genes reported in various studies which are associated with a bipolar genetic condition.

Though it’s a polygenic and complex genetic condition, it can be inherited from parent to offspring with a 10% chance of getting the condition. Nonetheless, the genetic basis and inheritance pattern are still not well-established and studied. 

More scientific studies, GWAS data and WGS data are needed to investigate and establish the genetic basis, if any. 

8. Learning and speech delay in DiGeorge syndrome:

Besides developmental delay, learning and speech disabilities are common among patients suffering from DiGeorge syndrome. The present condition shows a clear genetic foundation. 

Here deletion on chromosome 22 at 22q11.2; deletes 30 to 40 vital genes from the fetus, consequences show varying degrees of developmental, mental and cognitive problems. 

It shows clear genetic anticipation as the severity of signs and symptoms depends on how many portions of the chromosome get deleted and how many genes it loses. 

Notedly, a clear inheritance pattern is reported in only 10% of cases. 

Classic behavior psychology says that several behavioral traits are learned which can influence other morphological traits and are inherited in Mendelian patterns to offspring. 

Studying human behavior practically isn’t possible as it’s ethically restricted. However, commonly shared traits can be studied, for example, “rhythmic searching for a nipple.” This behavior is commonest among most mammals, however, it doesn’t have any significant genetic base. 

Some traits are more genetic and less learned and vice versa. For example, behavior patterns of deaf and blind people. Irrespective of their respective condition, expressions of anger, sharing and showing happiness and other facial expressions are common with normal people.  

Meaning, it probably does not have any genetic background but can’t be learned either (as these groups of people can’t either see or listen). Perhaps there might be some genetic factor behind that but yet not studied. 

Wrapping up:

As I mentioned earlier, psychological behavior is a complex trait group, learned, inherited, genetic, and influenced. Though some traits show defined genetic background, some are insignificant, but at the same time aren’t learned too. 

On the other hand, some traits are learned, genetic as well as inherited. Conclusively, we can say that psychological behavior and traits have a genetic base, but have not been studied yet or are less explored. 

I hope this article provides more clarity to this complex topic, comment below and let me know your thoughts on the present topic.

Sources:

Wan L, Li Y, Zhang Z, Sun Z, He Y, Li R. Methylenetetrahydrofolate reductase and psychiatric diseases. Transl Psychiatry. 2018;8(1):242. Published 2018 Nov 5. doi:10.1038/s41398-018-0276-6.

Kerner B. Genetics of bipolar disorder. Appl Clin Genet. 2014;7:33-42. Published 2014 Feb 12. doi:10.2147/TACG.S39297.

McDonald-McGinn DM, Hain HS, Emanuel BS, et al. 22q11.2 Deletion Syndrome. 1999 Sep 23 [Updated 2020 Feb 27]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2022. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1523/.

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