1. Chapter 3 Genes, Environment, and Development
Chapter 3 Genes, Environment, and Development

2. Species Heredity Genetic endowment Human examples
Species Heredity
Genetic endowment
Common to the species
Governs maturation and aging
Human examples
Two eyes, sexual maturity at yrs.
Natural Selection: Genes allowing adaptation are passed on

3. Evolution Charles Darwin (1809-1882) Main Arguments
Evolution
Charles Darwin ( )
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

4. 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

5. 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

8. 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

9. Genes: Their Location and Composition
Nucleus
Chromosome
Gene
Cell
DNA

10. Karyotype

11. Genes: Our Biological Blueprint
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

13. 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

14. 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

15. A genotype refers to person’s genetic heritage.

16. Phenotype
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).

18. Offspring with brown eyes

19. Sickle-Cell Anemia Caused by hemoglobin S that reduces O2
Caused by hemoglobin S that reduces O2
About 9% affected in U.S.
Homozygous recessive (ss)
Heterozygous: (Ss) “carriers”
Can transmit gene to offspring

20. 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

21. 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

22. Figure 3.2 The workings of sex-linked inheritance in red-green color blindness.
Figure 3.2

23. 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)

24. Errors in chromosome division: Meiosis
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

25. Trisomy 21

26. Down Syndrome (Trisomy 21)
Physical Deformities
flattening of the back of the head
slanting of the eyelids
short stubby limbs
thick tongues

27. Figure 3.3 The rate of Down syndrome births increases steeply as the mother’s age increases.
Figure 3.3

28. 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

29. Klinefelter syndrome: 1/200 males XXY, tall, sterile, feminine traits

30. FRAGILE X SYNDROME Leg of X barely connected Sex-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

32. 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

33. rapid, jerky involuntary movements
HUNTINGTON’S DISEASE
rapid, jerky involuntary movements
difficulty in speaking and swallowing
cognitive decline, depression, and occasionally delusions
hallucinations and obsessive compulsive disorders.

34. Behavioral Genetics Genetic/environment cause of trait
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

35. Figure 3.4 Correlations between the traits of identical twins raised apart in the Minnesota Twin Study.
Figure 3.4

36. 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)

38. 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

39. 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

40. Psychological Disorders
Schizophrenia concordance rates
MZ = 48%: DZ=17%
Affected parent increases risk: 13%
Inherited predisposition
Environmental factors – triggers
Prenatal exposure to infection suspected

41. 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.

42. 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

43. 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