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01.01 Behavioral Genetics

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Overview

  1. Behavioral Genetics
    1. Studies the differences between individuals
    2. Finds the interplay between genetics and environment
    3. Uses twin and adoption studies

Nursing Points

General

  1. Goal of behavioral genetics
    1. Studies the 1% DNA difference that individuals have from one another
    2. Looks to understand why some disorders happen to some people and not to others
  2. Genetics and environment
    1. Wants to explain how genetics and environment correlate
      1. Genetics = nature
      2. Environment = nurture
      3. Genetic factors can predispose an individual
      4. Environment can influence gene expression
    2. Uses twin and adoption studies
      1. Twin studies- biological studies
        1. Monozygotic (identical)
        2. Dizygotic (fraternal)
      2. Adoption studies
        1. Genetic factors
        2. Environment factors

Video Transcript

Hi everyone, this is Ashley and today we’re going to be talking about behavioral genetics.

Behavioral genetics is the study of how genetics and environment play a role in influencing the behavior of individuals. 99% of all of our DNA is identical but 1% is different. Behavioral genetics studies that 1%, that percent that makes use different from each other. It studies the “why”- why does one person have schizophrenia and another person does not? Why is one person an alcoholic and another is not? It studies how genetics and environment work together to create a difference in individuals.   

There is the famous nature vs nurture debate. Well,  it is not a debate. It is a discussion of nature and nurture. We know that both nature, or genetics, and nurture, environment, play a significant role in making up who we are. This includes our mental health, physical health, cognitive abilities, and personality. What we inherited and how we were raised, or the things that have happened to us, create who we are. We used to want to silo these and give one more credit than the other but we now understand them as both contributing to our personal outcomes.

Nature impacts nurture and nurture impacts nature. Let’s look at how each of these impacts the other more closely. Nature, or genetics, predisposes us to certain traits or characteristics. Let me be clear in that we now know that all things can be inherited. Even traits like vocabulary are inherited. This may sound strange, but we know that even though specific words are not passed down, we can see that vocabulary, catching onto subtleties and connotations, are inherited. We’ll come back to this in a second. While parents are raising their children, which is creating a certain environment, they are living through their own genetics. A parent that suffers from schizophrenia may parent differently, behave differently, or expose their child to different things than a parent without schizophrenia. That is an example of how nature can impact nurture.

The inverse of my original statement is also true, that nurture impacts nature as well. We know this because our environment can impact the expression of a gene and change our physiology. For example, if a child is raised in a home with high verbal expression, it will help develop their vocabulary and verbal expression, especially in those that are predisposed to significant vocabulary. We also know that experiences that happen to us can play a crucial role in changing our physiology. Studies indicate that a pregnant woman who is exposed to chronic stress, which would increase her stress hormone levels during that pregnancy, will significantly alter several things for the fetus, even having implications long after birth. This includes high levels of stress hormones in the baby, compromised gray matter, impaired white matter in the brain, and compromised immune system. The environment of the pregnant woman impacted the physiological aspects of the fetus. Studies support that a gestational environment can impact brain development function and structure and increase the long-term likelihood of neurodevelopmental and neuropsychiatric disorders. This is an example of how nurture, or our environment, can impact nature.


Behavioral genetics is primarily studied in two different ways. The first is through twin studies. Twin studies provide an opportunity to study biological factors that play into nature. Twin studies can be either monozygotic or dizygotic. Monozygotic twins are twins from one egg, or identical twins, exact same DNA. Dizygotic twins are fraternal twins and are no different genetically than any other siblings except they shared a womb. The Maudley twin studies are a good example. This ongoing study looks at cognition, memory, and brain structure in twins with and without certain diagnoses like bipolar and schizophrenia.  The Maudley studies support heritability estimates to be substantial for schizophrenia.

The second way to study behavioral genetics is through adoption studies. Adoption studies provide us with an opportunity to look at those that are genetically related, how a biological family member and child are similar and different, while also looking at those that are environmentally related, the adoptive family members and the child that was adopted at birth. Adoption studies generally support that twins separated at birth and reared in separate homes have about an equal chance of similarity as those that were reared in the same home in terms of personality, interests, and attitudes.

Alright, we’ve gone over a quick overview of behavioral genetics. The main key points to remember are that the stud of behavioral genetics focuses on the differences or the 1% between people. It focuses on “why this person and not another person?”. The most important key point though: that nature and nurture matter.

We love you guys! Go out and be your best self today! And as always, Happy Nursing!

 

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