Genetics & Nature vs. Nurture

Nature vs. NurtureIs there a biological reason why girls tend to like dolls and

clothes? Is there a biological reason why boys tend to like toy cars and guns? Or is this something that children are nurtured

to like by their parents and other societal factors?

Nature vs. NurtureWhy are women less interested in certain jobs? Is it because of

their genes, hormones, or biology? Or is it because they are nurtured into certain career paths by friends, parents, movies,

media, and other societal factors?

Careers with Many Women:

NursesSecretaries

Preschool/Kindergarten TeachersFlight Attendants

WaitressesSocial Workers

Careers with Few Women:

SurgeonsComputer Programmers

ChefsFirefighters

Aircraft PilotsEngineers

Nature vs. Nurture DebateNature:

Our genetics determine our behavior. Our

personality traits and abilities are in our

“nature.”

Nurture: Our environment, upbringing, and life

experiences determine our behavior. We are “nurtured” to behave

in certain ways.

Nature vs. Nurture DebateNature:

We genetically inherit physical traits from our

parents, but we also inherit personality traits,

intelligence, and preferences.

Nurture: The household and city we grew up in, how we were

raised by our parents, teachers, and friends -

these are environmental factors that determine

who we are.

Nature vs. Nurture Debate

A Point for Nature: “Studies show that

we inherit genes that are related to certain

personality traits.”

A Point for Nurture: “Often Identical twins

grow up to have very different

personalities and preferences.”

?

Nature vs. Nurture Debate

Today we know that nature and nurture BOTH help shape our behavior. The question

for today’s debate is this:

Which one has the GREATER influence on human behavior?

Pair-ShareDo you think you share any personality traits

with your parents or grandparents?

Behavioral Genetics:The study of the effects of heredity on behavior.

Behavioral genetics tries to answer this question: To what extent are our abilities, personality traits, sexual

orientations, sociability, and psychological disorders determined by genes inherited from our parents?

Will this child be

more like her birth

parents or adoptive parents?

Twin StudiesTwin Studies are used to help us answer the question of “nature

vs. nurture.” Because identical twins share the same genetic makeup, we can assume that differences between them are due

to environmental factors.

Twin Studies Pair 1:

Same DNASame Environment

However, twins often grow up in very similar environments.

If intelligence is the same, it’s hard to tell if it is due to genetics or

environment.

Pair 2:Same DNA

Same Environment

If intelligence is different, we can assume that there are tiny

differences in environment (different friends, time spent studying, etc.)

that caused the difference.

Twin Studies Pair 4:

Different DNASame Environment

One sibling is adopted.If intelligence is the same,

it is likely due to environment. If intelligence is different, it is

likely due to genetics.

Pair 3:Same DNA

Different Environment

Twins adopted by different families grow up in different environments.

If intelligence is the same, it is likely due to genetics. If intelligence is different,

it is likely due to environment.

Twin Study Results?

Extraverted

Neurotic

Agreeable

Conscientious

Correlation (How strongly twins shared the same traits)

0 0.1 0.2 0.3 0.4 0.5

Identical Twins (99% DNA match) Fraternal Twins (50% DNA match)

Open to New Experiences

Pair-ShareDo you think a Twin Study is a reliable way to

test whether our behavior is determined more by nature (genetics) or nurture (environment)?

Why or why not?

What do studies tell us?

Study: 1,252,387 genetic markers were tested for

association with personality traits. The results indicated

that only 1% of genetic variants significantly

contribute to personality variation. This means our

individual genetic differences do not significantly contribute to personality trait variation.

(Verweij et al., 2010)

Personality:

What do studies tell us?

Study: 1,252,387 genetic markers were tested for

association with personality traits. The results indicated

that only 1% of genetic variants significantly

contribute to personality variation. This means our

individual genetic differences do not significantly contribute to personality trait variation.

(Verweij et al., 2010)

This was NOT a twin study: it was a genome-wide association study done in 2010. This is

where each person gives a sample of DNA, from which millions of genetic variants are read in order to see if certain genes are associated with diseases

or personality traits.

Other Studies That relate to the “nature, nurture” question

Study: Men who carry one or two extra copies of a gene called allele 334 often behave differently in relationships

than men who lack this gene variant. Men with an extra copy of the gene felt a weaker, less permanent attachment

to their partners, and were more likely to be unfaithful. Men who had two

copies of allele 334 were also twice as likely to have had a marital or

relationship crisis in the past year than those who lacked the gene variant.

(Karolinska Medical Institute, Stockholm).

Nature? (Genetics) or Nurture? (Environment)

Study: Novelty-seeking

behavior (impulsive decision-making, the need to explore, lack

of organization) is related to the

presence of a certain gene in the body, and is highly inheritable.

(Golimbet et al., 2007).

Other Studies That relate to the “nature, nurture” question

Genes & Test ScoresIn a recent study at University college London, researchers

compared test scores of high school students to their genes. The study found that 58% of the variation on student test

scores was due to genetic factors.

The research drew on the exam scores of more than 11,000 16-year-olds. Researchers also compared the scores of identical and non-identical twins in a supplementary study.

Genes & Success Does having amazing genes lead to future

career success and wealth?

This boy had genius parents.

Do you think his genes will have a greater

impact on his life, or his environment?

Genes & SuccessStudies show that for children living in poverty, it did not matter whether

they had good genes or not. The negative impact of the environment almost always played a greater role in their future success than their

genes.

For children in middle class and wealthy homes, having good genes

became very important to determining their future success.

Genes played a much greater role in the future success of each child.

Genes & Success

Researchers concluded that for children in harsh living conditions, it is harder for exceptional genes to “shine through.”

(Eric Turkheimer, 2003)

Feral Children

Feral Children are those who lived away from human contact

from a very young age, and have little or no experience of human care,

loving or social behavior, or

human language.

Feral ChildrenHomework:

Investigate it yourself:What can we learn from Feral

Children about nature vs. nurture?

Research at least one feral child, and write a paragraph (at least 5

sentences) about what feral children can teach us about

nature vs. nurture.

Submit by sharing a google doc with Ms. G before the start of

our next class.

Examples: Genie Wiley

Oxana Malaya Kamala & Amala Prava the Bird Boy

…

Nature vs.

Nurture: Epigenetics

Epigenetics is a new field showing

us that environment can modify our genes!

EpigeneticsThis is a new branch of genetics that is shedding light

on the “nature vs. nurture” debate. “Epi” means “above” or “on top of” so epigenetics refers to

modifications that occur on top of your genes. Environmental factors actually cause your cells and genetic code to change

over your lifetime. Your genetic code itself is always the same, but genes can be “turned on” or “turned off.”

For example, your diet can cause “epigenetic changes” to your DNA.

Epigenetics

different clothing styles. Their personalities became different: "Mary is more conscientious about what she does. I am more confident. That became increasingly obvious as the years went by," says Barbara. Mary developed depression, Barb did not. Mary was girly and feminine, Barbara was more of a “tomboy.”

HERES WHAT HAPPENED TO THEIR GENES…

Mary and Barbara are identical twins raised in the same family. When they were kids, their parents treated them the same and they had similar interests and personalities. However, the older they became, the more different they became. They dressed in

Epigenetics

The DNA of the twins began the same, but over the course of their lives, different health choices and environmental stimuli

caused the DNA code to change.

Epigenetics

This is a strand of DNA.

DNA is a long, ladder-shaped molecule: the famous ‘double-helix’

shape. Inside our cells, DNA contains all the information needed

to make us grow and live.

EpigeneticsGenes are short sections or

“chunks” of DNA.

They act as a set of instructions for our

cells, telling them how to build our bodies.

EpigeneticsThroughout your life, and

depending on specific conditions, a chemical called

methyl attaches to genes. This chemical “switches” on

or off only a selection ofyour genes.

This process is known as gene regulation.

EpigeneticsThese chemical methyl attachments are called epigenetic

tags.

EpigeneticsThese chemical methyl attachments are called epigenetic

tags.

Think of them like switches that turn certain genes on or off, making them active or inactive.

Epigenetics

Your lifestyledetermines which

genes get “switched on” or “switched off.”

What (and how much) you eat, how much you exercise, if you smoke, if you get a disease, if you experience high stress, if you are exposed to

chemicals, etc…can all impact the way your genes are expressed.

Epigenetics

During fertilization, mom & dad’s DNA mixes in the egg.

During the first days after fertilization, the epigenetic tags are

erased…mostly.

A small number of tags remain on the offspring’s DNA.

EpigeneticsBecause a small number of tags remain on the

offspring’s DNA…

…these are called “imprinted

genes.”

Epigenetics

Thus, the environment and lifestyle choices of

the parents actually modified the genetic

code of their offspring.

Stress Gene Experiment

Experimental Group 1:Baby rats are nurtured

by a mother rat

Experimental Group 2:Baby rats are neglected

by a mother rat

?

Stress Gene Experiment

Group 1:The babies’ DNA is tested

and epigenetic tags are visible on the stress

response gene, turing it “on.” These rats respond

very well in stressful situations for the rest of

their lives.

Group 2:The babies’ DNA is tested

and epigenetic tags are NOT present on the stress response gene, keeping it “off.” These rats do NOT respond well in stressful situations for the rest of

their lives.

Stress Gene Experiment

Group 1:The offspring of these rats ALSO have epigenetic tags

on the stress response gene: the babies inherit an imprinted gene on which

the stress response gene is “turned on.”

Group 2:The offspring of these rats ALSO have NO epigenetic tags on the stress response gene. Thus, these babies do not respond well to stress because their PARENTS were not nurtured by a

mother rat.

Inherited Stress Tolerance?

The rats that were not nurtured as babies had the stress response gene

“turned off.” In this case, the rats could not handle stressful situations well for the rest of their lives. They

also passed this inability to respond to stress to their children.

This study shows that attentive, loving parents set their children (and grandchildren!) up for future success by

creating an epigenetic modification that allows the children to better cope with stress. The environment can change our genes, and our genes impact certain aspects of our behavior.

Are Epigenetic Changes Permanent?

EpigeneticsQ: What does this mean for the nature vs. nurture debate?

(1)That we are not defined by our genes. Our lifestyle choices can actually impact our genetic codes, causing certain genetic traits to

express themselves more or less strongly.

(2)That the interaction between nature and nurture is WAY more complicated than we ever imagined. Genes and environment are

always working together.

This does not mean that we have the power to change all of our genes! Some genes are not modifiable, meaning that epigenetic tags

do not affect those genes.