1-02 The Genetic Of Behavior (Part 1)

Front 1

Objective

Identify two types of evidence that researchers use to study heritability.

Back 1

1. Twin studies compare monozygotic (identical) and dizygotic (fraternal) twins. A stronger resemblance between monozygotic than dizygotic twins suggests a genetic contribution.

2. Adoption studies compare the traits of adopted children with biological and adoptive parents. Any tendency for adopted children to resemble their biological parents suggests an hereditary influence.

Front 2

Objective

Give examples of ways in which genes affect behavior.

Back 2

1. Directly: predisposing the individual to certain behaviors, such as those related to mental illness, criminal activity, and high- or low-intelligence.

2. Indirectly: by changing one’s environment in ways that might magnify certain tendencies. For example, suppose your genes lead you to frequent temper tantrums. Other people—including your parents—will react harshly, giving you still further reason to be hostile. This is called a multiplier effect.

Front 3

Objective

Explain why it is difficult to distinguish between heredity and prenatal influences.

Back 3

Parents provide children with their genes and their prenatal environment. That makes it difficult to determine if children’s behavior is due to their genetic makeup or the environment in which they were conceived and raised.

Front 4

Objective

Discuss the relationship of heredity and environment in PKU.

Back 4

Although phenylketonuria (PKU), a genetic inability to metabolize the amino acid phenylalanine, is a hereditary condition, environmental interventions can modify it. For example, if a baby has high levels, indicating PKU, physicians advise the parents to put the baby on a strict low-phenylalanine diet to minimize brain damage (diet includes: avoiding meats, eggs, dairy products, grains, and especially aspartame (NutraSweet), which is 50% phenylalanine). Our ability to prevent PKU provides particularly strong evidence that a heritable trait is not necessarily unchangeable.

Front 5

Chromosome

Back 5

A strand of DNA found in the cell nucleus; Carries genetic information

Front 6

Gene

Back 6

Functional unit of the chromosome, which directs the synthesis of proteins

Front 7

Deoxyribonucleic acid (DNA)

Back 7

The basic genetic material that serves as a template (model) for the synthesis of ribonucleic acid (RNA) molecules

Front 8

Ribonucleic acid (RNA)

Back 8

Single-strand chemical; One type of RNA molecule serves as a template for the synthesis of protein molecules

Front 9

Enzyme

Back 9

Biological catalysts that regulate chemical reactions in the body; They are molecules that combine two substances or break substances into two parts

Front 10

Homozygous

Back 10

Identical pair of genes on the two chromosomes

Front 11

Heterozygous

Back 11

Unmatched pair of genes (e.g. you might have a gene for blue eyes on one chromosome and a gene for brown eyes on the other)

Front 12

Dominant gene

Back 12

Gene that shows a strong effect in either the homozygous or heterozygous condition

Front 13

Recessive gene

Back 13

Gene that shows its effects only in the homozygous condition

Front 14

Crossing over

Back 14

A pair of chromosome may break apart during reproduction and reconnect such that part of one chromosome attaches to the other part of the second chromosome

Front 15

Sex-linked gene

Back 15

Genes located on the sex chromosomes; All other chromosomes are autosomal chromosomes (non-sex chromosomes)

Front 16

Autosomal gene

Back 16

Genes on autosomal chromosomes

Front 17

X & Y chromosomes

Back 17

Sex chromosomes; Most mammals have one pair of sex chromosomes in each cell; Males have one Y chromosome and one X chromosome, whereas females have two X chromosomes

Front 18

Sex-limited gene

Back 18

Genes present in both sexes but have effects mainly or exclusively for one sex; Genes control such characteristics as the amount of chest hair in men and breast size in women; Both sexes have those genes, but sex hormones activate them, so their effects depend on male or female hormones

Front 19

Recombination

Back 19

A new combination of genes, some from one parent and some from the other, that yields characteristics not found in either parent; For example, a mother with curly blonde hair and father with straight black hair could have a child with curly black hair or straight blonde hair

Front 20

Mutation

Back 20

Change in a single gene; For example, a gene for brown eyes might mutate into a gene for blue eyes

Front 21

Monozygotic twins

Back 21

Identical twins (from one egg)

Front 22

Dizygotic twins

Back 22

Fraternal twins (from two eggs)

Front 23

Heritability

Back 23

Degree to which variations in some characteristic depend largely on hereditary influences; High heritability—largely affected by heredity, low heritability—minimally affected by heredity

Front 24

Multiplier effect

Back 24

If genetic or prenatal influences produce even a small increase in some activity, the early tendency will change the environment in a way that magnifies that tendency

Front 25

Phenylketonuria (PKU)

Back 25

A genetic inability to metabolize the amino acid phenylalanine; If PKU is not treated, the phenylalanine accumulates to toxic levels, impairing brain development and leaving children mentally retarded, restless, and irritable