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Genotype and Phenotype

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Genotype and Phenotype

There is only one of you on this planet your DNA is unlike anyone else's; it is unique. Even genetically identical twins differ in appearance and behaviour.

But what is it that distinguishes us? That is where the concepts of genotype and phenotype come into play. We'll quickly go over those to clarify any differences between the two before delving deeper into the examples and their significance in psychology.

The genotype is the genetic basis of an organism. It consists of all the genetic information that determines the characteristics of organisms.

The phenotype is the observable expression of these genes. The environment influences the phenotype.

An excellent way to remember this is to think of genotype as referring to the internal genetic makeup unique to each person and phenotype as the physical, observable expression of that information.

An example of a genotype would be a person's skin composition and the amount of melanin (a skin pigment) they produce. An example of a phenotype would be the darkening of the skin due to UV radiation.

Genotype and Phenotype [+] Examples [+] StudySmarter

Genotype and phenotype examples, StudySmarter Originals (Images from Flaticon and Canva)

Genotype

Genotype refers to the genetic basis of an organism.

The DNA that we are born with is an example of a genotype.

The genotype is critical to developing the phenotype, but the environmental forces that determine the phenotype can often cause even genetically identical people (like identical twins) to have significant differences.

Twin studies allow us to determine how much genotype influences human behaviour. These studies look at groups of twins and their behaviour. Because twins are so genetically similar (100% genetic match for monozygotic twins and 50% for dizygotic twins), these study results allow us to measure and assess the genetic basis of behaviour.

Coccaro (1997) is an example of these twin studies. Coccaro examined the criminality of groups of monozygotic twins and some dizygotic twins. Monozygotic twins happened to have similar concordance rates in criminality compared to the dizygotic twins. This finding suggests a genetic component to behaviour, as the more genetically similar twins exhibited a more significant similarity in behaviour.

Research on specific genes also exists. Tuart et al. (2014) found that of 97 participants (all men) who had severely physically abused their romantic partners, men who happened to have a dysfunctional version of a gene known as MAOA committed the worst, most violent, and sadistic acts. These findings suggest that genes may have a direct influence on aggressive behaviour.

As this evidence shows, genetic predisposition plays a role in psychological development and behaviour in humans. However, we cannot talk about genotype without discussing phenotype and the difference between the two.

Genotype and Phenotype [+] Tuart et al. (2014) MAOA gene influences aggressive behaviour [+] StudySmarter

Tuart et al. (2014): MAOA gene's direct influence on aggressive behaviour, StudySmarter Originals (Images from Flaticon and Canva)

Phenotype

Phenotype is the observable, measurable expression of an organism's genes influenced by the environment.

An example of a phenotype would be your height because environmental factors such as diet affect growth.

In psychology, an example of a phenotype would be how environmental factors such as home life in childhood can affect how people develop and behave in adulthood. For example, Caspi et al. (2002) found that study participants who exhibited more violent behaviour not only had a dysfunctional MAOA gene but also experienced an abusive childhood. Thus, the genotype of the dysfunctional MAOA gene may not have been the sole cause of the violent behaviour, but rather the expression of this gene when exposed to violent situations.

Why is the distinction between genotype and phenotype important?

We need to distinguish between genotype and phenotype to understand the extent to which human behaviour is determined by internal, genetic factors (genotype) or by environmental influences and situations in which observable traits and behaviours arise (phenotype). It is usually a mixture of genetic factors (genotype) and environmental factors that affect how these genes are expressed (phenotype), leading to behaviour changes.

How might the distinction between genotype and phenotype help with mental health issues?

Understanding the differences between genotype and phenotype can also help us understand inherited traits.

A family may have a genetic predisposition to developing depression or another mental health problem, but they can avoid developing symptoms with the proper treatment or environment.

It is essential to distinguish between genotype and phenotype here because:

  • Some people are born with a genetic predisposition to developing mental health problems.
  • Some develop them as a product of their environment.
  • A combination of both.

Their treatment can be tailored to their circumstances.

The distinction between genotype and phenotype can help doctors use their resources more effectively when it comes to mental health. A patient with a family history of mental health problems may be more likely to suffer from a chemical imbalance in the brain that responds better to medical treatment than therapy.

Conversely, a patient with no known family history of mental health problems and whose mental health problems are a product of their environment may help physicians determine what elements of their environment have affected them and how. This approach can help with therapeutic techniques such as Cognitive Behavioural Therapy (CBT) and Dialectical Behavioural Therapy (DBT).


Genotype and phenotype - Key takeaways

  • Genotype is the genetic makeup of an organism.
  • Genes can affect behaviour, such as the MAOA gene.
  • Phenotype is the visible result of the interaction between the environment and the genetic makeup.
  • It is essential to distinguish between genotype and phenotype to understand the origins of behaviour.
  • Understanding the difference between genotype and phenotype helps treat mental health problems.

Frequently Asked Questions about Genotype and Phenotype

Genotype is the genetic information found in DNA, while phenotype is the physical, observable result of genotype, such as black hair.

Observing the genetic makeup of an organism can allow one to determine the genotype while observing the physical characteristics of an organism can allow one to determine the phenotype.

For example, the genotype that codes for seeds to be yellow would be written as YY, yy. The phenotype is written as the characteristic that the genotype codes for. In this case, you would write the phenotype as ‘yellow seed colour’.

Phenotype requires genotype to exist, as it is a combination of genotype and environmental influences.

Final Genotype and Phenotype Quiz

Question

What is a genotype?

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Answer

Genotype refers to the genetic makeup of an organism.

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What is phenotype?

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Answer

Phenotype refers to the result of genes interacting with the environment.

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What is the difference between genotype and phenotype?

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Answer

Genotype influences phenotype, but the phenotype is not the same as genotype. Phenotype is the result of genes interacting with the environment.

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Question

What is an example of a genotype?

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Answer

An example of a genotype is DNA.

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What is an example of phenotype?

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An example of phenotype is a person’s height.

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What is an example of a genotype affecting behaviour?

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Answer

MAOA is an example of a genotype affecting behaviour. Specifically, MAOA influences aggression.

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What is an example of environmental factors influencing behaviour?

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Answer

An example of environmental factors influencing behaviour is how childhood can affect behaviour.

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True or false: Behaviour is the result of both genetics and the environment.

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Answer

True.

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Why are twin studies useful when studying genotype and phenotype?

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Answer

Monozygotic twins are genetically identical, so twin studies allow us to see the effects of the environment on their phenotype.

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What did Coccaro (1997) find out about the behaviour of monozygotic twins?

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Answer

Coccaro found that concordance rates of criminality were closer in those with greater genetic similarity.

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What does Coccaro’s study suggest about genes and behaviour?

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Answer

Coccaro’s study suggests that there is a link between genetics and behaviour.

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True or false: Caspi et al. prove a link between environment and behaviour.

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True.

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How does genotype affect mental health?

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Answer

Some families have a history of mental health issues that they may pass down through genetics.

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How does phenotype link to mental health?

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Phenotype is based partly on the environment someone lives in, so the environment may adversely affect mental health.

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Question

Why is it important to distinguish between genotype and phenotype? 

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Answer

An example of applying this distinction in psychology would be the treatment of mental health issues.

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