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0. Chapter 3 Genes, Environment, and Development. 0. Species Heredity Genetic endowment Common to the species Governs maturation and aging Human examples Two eyes, sexual maturity at 12-14 yrs. Natural Selection: Genes allowing adaptation are passed on. 0. Evolution.

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Chapter 3Genes, Environment, and Development


  • Species Heredity

    • Genetic endowment

      • Common to the species

      • Governs maturation and aging

    • Human examples

      • Two eyes, sexual maturity at 12-14 yrs.

    • Natural Selection: Genes allowing adaptation are passed on




  • Charles Darwin (1809-1882)

    • Species characteristics

      • How they change over time

  • Main Arguments

    • Genetic variation exists in all species

    • Some genes aid in adaptation

  • Kettlewell’s Moths: Genetic variability provides for adaptation

Modern evolutionary perspectives


Modern Evolutionary Perspectives

  • What we do today was adaptive for ancestors

  • Example: mothers invest more in child rearing

    • Maternity is certain; paternity may not be

  • Evolution: gene/environment interaction

    • Traits are demanded by environment

    • Advantageous genes for a particular environment survive

Individual heredity the genetic code


Individual Heredity - The Genetic Code

  • Zygote: union of sperm and egg

    • 23 pairs of chromosomes

    • Each pair influences one characteristic

    • Pair: One from father one from mother

  • Meiosis: produces sperm and ova

  • Mitosis: cell-division process

    • Creates new cells

Genes our biological blueprint
Genes: Our Biological Blueprint

  • Chromosomes

    • threadlike structures made of DNA that contain the genes

  • DNA (deoxyribonucleic acid)

    • contains the genetic information that makes up the chromosomes

    • has two strands-forming a “double helix”--held together by pairs of nucleotides

Genes their location and composition






Genes: Their Location and Composition

Genes our biological blueprint1
Genes: Our Biological Blueprint

  • Genes

    • biochemical units of heredity that make up the chromosomes

    • a segment of DNA synthesizes a protein

  • Genome

    • consisting of all the genetic material in its chromosomes

Genetic uniqueness relatedness


Genetic Uniqueness & Relatedness

  • Monozygotic (MZ) twins: 100% related

    • 2 genetically identical individuals

  • Dizygotic (DZ) twins: 50% on average

    • 2 ova fertilized by 2 sperm

  • Siblings: 50% on average

  • Parent & Child: 50% related, shared

  • Males: XY; Females: XX

Translation of the genetic code


Translation of the Genetic Code

  • Genes provide instructions for development

    • Eye color and other characteristics

    • Regulator genes turn on/off gene pairs

      • Adolescent growth spurt

      • Shut down some in adulthood


A genotype refers to person’s genetic heritage.


  • The phenotype is one’s genotype expressed in characteristics that can be observed and measured.

  • It includes physical traits (e.g., height, weight) as well as psychological characteristics (intelligence, personality).


Offspring with brown eyes

Sickle cell anemia
Sickle-Cell Anemia


  • Caused by hemoglobin S that reduces O2

  • About 9% affected in U.S.

    • Homozygous recessive (ss)

  • Heterozygous: (Ss) “carriers”

    • Can transmit gene to offspring

Sickle cell anemia1
Sickle-Cell Anemia


  • Incomplete dominance – carriers show signs of having recessive trait

    • Will not have the disease, but sickling episodes

  • Co-dominance – neither gene in pair is dominant or recessive

Sex linked inheritance


Sex-Linked Inheritance

  • Single genes located on sex chromosomes

  • Actually X-linked

  • Males have no counterpart on Y chromosome

  • Females have counter on second X

    • Requires gene on both X’s for trait

  • Hemophilia, Colorblindness

Figure 3 2


Figure 3.2

Polygenic inheritance and mutations
Polygenic Inheritance and Mutations


  • Polygenic: Most human characteristics influenced by multiple genes

    • Height, weight, intelligence, temperament

  • Mutations: Change in structure/arrangement of genes

    • Environmental hazards (teratogens) can cause mutations

    • Produces new phenotype

    • Sperm more likely than ova

    • Harmful or beneficial (e.g., sickle-cell protects from malaria)


  • Errors in chromosome division: Meiosis

    • Too many or too few chromosomes

  • Most spontaneously aborted

  • Down syndrome: Trisomy 21

    • Physical deformities (eyelid folds, short stubby limbs, thick tongues)

    • Mental retardation

    • Related to age of mother

Down syndrome trisomy 21
Down Syndrome (Trisomy 21)

  • Physical Deformities

flattening of the back of the head

slanting of the eyelids

short stubby limbs

thick tongues


Figure 3.3

Turner syndrome single x chromosome xo
TURNER SYNDROME (Single X chromosome - XO)

1/3000 females - short stature, sterile, webbed neck, stubby fingers, arms that turn out slightly at the elbow, and a low hairline in the back of the head

Klinefelter syndrome 1 200 males xxy tall sterile feminine traits
Klinefelter syndrome:1/200 malesXXY, tall, sterile, feminine traits

Fragile x syndrome leg of x barely connected sex linked affects mostly males
FRAGILE X SYNDROMELeg of X barely connectedSex-linked: affects mostly males

eye & vision impairments Hyper-extensible joints (double jointed)

elongated face Large testicles (evident after puberty)

Flat feet Low muscle tone

High arched palate Autism and autistic-like behavior

Prominent ears hand biting and hand-flapping

Mental Retardation Hyperactivity and short attention span

Genetic diagnosis and counseling


Genetic Diagnosis and Counseling

  • Tay-Sachs disease

    • Cause: recessive gene pair

    • European Jews/French Canadians

  • Huntington’s Disease

    • Single dominant gene

  • Learn about risk to unborn child

  • Learn about nature, inheritance and effects of genetic disorders in family history

Huntington s disease

rapid, jerky involuntary movements

difficulty in speaking and swallowing

cognitive decline, depression, and occasionally delusions

hallucinations and obsessive compulsive disorders.


Behavioral genetics


Behavioral Genetics

  • Genetic/environment cause of trait

  • Heritability estimates (genetic)

  • Methods of studying

    • Experimental and selective breeding – attempt to breed particular traits into animals

      • Tryon’s maze-bright rats indicate that activity level, emotion, sex drive may have strong genetic basis

    • Twin, adoption, family studies

      • Reared together or apart

      • Concordance rates


Figure 3.4

Estimating influences


Estimating Influences

  • Genetic similarity

    • Degree of trait similarity in family members

  • Shared environmental influences

    • Living in the same home

  • Non-shared environmental influences

    • Unique experiences (e.g., emotionality)


Accounting for individual differences


Accounting for Individual Differences

  • Correlations highest in identical twins

    • Genetic factors determine trait

  • Correlations higher if twins reared together

    • Environmental factors

  • Correlations are not perfect

    • Non-shared experiences

  • Identical twins more alike with age

Temperament and personality


Temperament and Personality

  • Temperament – set of tendencies concerning emotional reactivity, activity, and sociability (genetic)

  • Temperament correlations

    • MZ twins = .50 to .60

    • DZ twins = 0

  • Personality correlations similar

    • DZ shared environment unimportant

    • Same home - different personalities

    • Non-shared environment and genes important

Psychological disorders
Psychological Disorders


  • Schizophrenia concordance rates

    • MZ = 48%: DZ=17%

    • Affected parent increases risk: 13%

  • Inherited predisposition

    • Environmental factors – triggers

    • Prenatal exposure to infection suspected

Gene environment correlations


Gene/Environment Correlations

  • E.g., Sociable genes

    • Passive G/E correlations – parents’ genes influence the environment they provide for children, as well as the genes the child receives

      • Parents create social home

    • Evocative G/E correlations – child’s genotype evokes certain reactions

      • Smiley baby gets more social stimulation

    • Active G/E correlations – child’s genotype influences the environment that he/she seeks

      • Child seeks parties, friends, groups, etc.

Genetic influences on environment


Genetic Influences on Environment

  • Finding: Parents who read to their children have brighter children. Why?

    • Environment: reading to child makes them brighter

    • Genetic: brighter parents more informed or they enjoy reading themselves

  • Finding: Aggressive children have hostile parents.

    • Genetic: inherited behaviors

    • Environment: growing up with negative, hostile parents causes the behavior

Controversies surrounding genetic research


Controversies Surrounding Genetic Research

  • Identification of carriers of diseases and disorders

  • Giving information which leads to abortion

  • Experimenting with techniques for genetic alteration

  • Better parenting if child’s genetic predispositions understood