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Heredity: Our Genetic

• Heredity is transmission of characteristics from parents to offspring- Physical traits – height, hair, & eye

color- Psychological traits like – shyness,

leadership, & aggressiveness; interested in arts & crafts

• Disorders such as anxiety, depression, schizophrenia, bipolar disorders, & alcoholism

Genes & Chromosomes

• Genes are the basic building blocks of heredity- Traits are pairs of genes, with one gene in

each pair inherited from each parent* Blood type (single pair of genes);

Intelligence (combinations of genes)• Chromosomes found in DNA

- Most normal human beings have 46 chromosomes (organized into 23 pairs)

- Psychologists try to find clues of psychological traits in how genes are paired* Without 46, physical & behavioral

disorders result

Nature-Nurture Debate

• Nature refers to what people inherit – biological groundwork that prepares a person to develop in certain ways.

• Nurture refers to environmental factors – what a person is exposed to in life; family, education, culture, living conditions, & everyday individual experiences

• How much of who we are is found in our genes (nature) verses how we are raised & environmental conditions (nurture)?

How Much Do You Have In Common With Your Relatives?• Identical Twins: 100% of their genes• Parents & Children: 50% of their genes• Brother & Sisters: 50% of their genes• Your Aunts & Uncles: 25% of their

genes• Your 1st Cousins: 12.5% of their genes

Human Behavior Genetics

• Family Studies based on the assumptions that if genes influence a trait, close relatives should share that trait more often than distant relatives because close relatives have more genes in common.- For example, schizophrenia occurs in only 1 to

2% of the population. Siblings of schizophrenia are about 8 times more likely, & the children are about 10 times more likely, to develop the disorder.* However, families also share environments.

Twin Studies & Fraternal Twin Studies

• Twin studies & fraternal twin studies have provided evidence for the habitability of a # of behaviors, ranging from verbal skills to aggressiveness, to mannerism such as the strength of a handshake to depression & anxiety.- For example, when one identical twin develops

schizophrenia, the chances that the other twin will develop the disorder are about 50%. For fraternal twins, the chances are about 15%.* The higher rate exhibited by twins, particularly

identical twins, suggests that heredity plays a crucial role in schizophrenia.

Adoptive Studies

• Adoptive studies focus on children who were adopted at birth & brought up by parents not genetically related to them, & evidence for the habitability of intelligence & some forms of mental illness & in behavior thought to be solely determined by environmental influences.- For example, of the 47 people whose

adopted mother suffered from schizophrenia, 5 adoptees subsequently suffered as well.* With a control group, however, there was

not a single case.

Record both psychological & physical traits that you share with members of your family! Identify if the traits are nature or nurture.

Psychological & Physical Traits

Heredity: Nature Environmental: Nurture

1. Color of my eyes *

2. Work ethic *

3. Height *

4. Personality * *

5. Sense of Humor *

6. Hair Color *

7. Athleticism *

8. Physical Make-up *

9. Intelligence * *

10. Determination * *