1. The Human Heritage: Genes and the Environment

2. Nature/Nurture First coined by Richard Mulcaster (1582)
Refers to the ‘twin forces on development’
Biological and environmental influences
Nature
Inborn biological endowment
Nurture
environment within which development occurs
Interaction of Forces

3. Sexual Reproduction and Genetic Transmission
Chromosomes
Single molecule of DNA, thousands of genes
= zygote
Genes
segments of DNA, double helix, ladderlike
blueprint for synthesis of protein molecule
units of heredity

5. Sexual Reproduction and Patterns of Heredity
The basics
somatic cells hold genetic info on copies of 46 chromosomes inherited at conception
Chromosomes dispersed throughout the nucleus
23 pairs of chromosomes
22 autosomes, 1 sex chromosome
males xy
females xx

6. Cell Division: Somatic Cells
Mitosis
for somatic (body) cells
each cell replicates itself, then divides
result is two cells identical to original

8. Cell Division: Germ Cells
Meiosis
for germ cells
replication with 3 processes to ensure resulting cell is nonidentical to germ cells (genetic diversity: chances are 1/70 trillion)
2 steps of division
crossing over
random pairing during 2nd division
monozygotic vs. dizygotic twins

10. Genotype/Phenotype Genotype Phenotype
the set of genes you inherit, your unique blueprint
Phenotype
how that set of genes is expressed as a result of the environmental stresses
the observable characteristics

11. Environment Genetic code is expressed in environments
Multi-levels of influence possible (egs.)
prenatal hormonal environment
chemical environment of the cell
nutrition of mother during pregnancy
stress of mother
opportunity for physical exercise
birth order as it relates to attention from parent

12. Not Exactly Identical

13. Mendel’s Laws of Inheritance
Definitions of terms
locus
homozygous
heterozygous
allele
dominant
recessive
intermediate expression of trait

14. Laws of Inheritance
Discrete traits inherited on the basis of allele information from a single locus
Chin cleft
Blood type
Polygenetic traits inherited as result of information from several genes
Verbal skill
shyness

15. Codominance: Result is distinct characteristics

16. Genetic Sex also Source of Variability

17. Sex Linked Genetic Effects: Red/Green Colorblindness
recessive trait
chances are 1/10 for males
chances are 1/100 for females
gene carried on x chrom, males have no complementary allele to compensate for the harmful effects

18. Gene-Environment Interactions
Behavioral geneticists study how genes and environment combine to influence organism’s development
Variations in environment can have large effects on development of phenotype
Gene-environment interaction is a two-way process
Genetic factors play a role in the environments that individuals inhabit and how they shape their environments

19. Range of Reaction: charting the change in phenotype as environment changes

20. Canalization: some characteristics restricted to narrow range despite wide variation in environment

21. Heritability: The study of genetic influences on behavior
Attempt to assess the degree to which variation among individuals on a given trait can be attributed to genetic as compared to environmental differences
e.g., weight - a physical trait
e.g., intelligence - a psychological trait
can factors in the environment influence weight or intelligence?

22. Heritability, cont’d
Degree to which variation among individuals on a particular trait can be attributed to genetic differences
h2 = variation due to genes
total variation
applies to groups and not to individuals
for clones, any variation has to be due to environment, thus h2=0
h2=1- variance accounted for by environment
heritability increases as genetic diversity increases and decreases as genetic diversity decreases

23. Heritability: Infant Temperament
This video from the laboratory of Hill Goldsmith shows part of a study about infant temperament. An object of desire is set in motion, first for each infant in a pair of fraternal twins and then for each infant in a pair of identical twins. Note how the twins react when prevented from reaching the desired object.

24. Heritability of Intelligence: History
Francis Galton’s Eminent Persons Study
tested idea that differences in intellectual achievement was due to genetic differences
basic flaw in logic is that eminent people also shared similar environment as well as gene pool
first to use adoptive method in study of boys adopted by RC Popes; found little evidence that environment affected eminence
Recommendations made for selective breeding, as they were to be made later by Hitler
Interesting aside: Darwin’s cousin

25. Heritability of Intelligence: Kinship Studies
Twin Methods
correlations among IQs of pairs of people related to different degrees, e.g., identical twins, dizygotic twins, siblings,
Adoptive Methods
correlations among pairs of people who share an environment but not genes, e.g., adopted child and biological child

26. Intelligence: The Findings
Identical twins raised apart .72
Identical twins raised together .86
Same sex twins raised together .62
Diff sex twins raised together .57
Siblings
Unrelated siblings

27. Heritability of Schizophrenia
Adoption Studies
e.g., Kety et al (1976) found strong evidence of heritability
only biological relatives of adoptee who is schizophrenic show high incidence of schizophrenia

28. Heritablity of Schizophrenia
Twin Studies
High concordance for identical twins, this concordance deceases as genetic relatedness decreases
Identical twins 48% concordance
Fraternal twins 17%
Siblings 9%
Half-sibling 6%
Fisrt cousin 2%
Child of two sch. Parents 46%
Child of one sch. Parent 13%

29. Mutations and Genetic Abnormalities
Mutations are errors in the process of gene replication; can be positive but usually negative
Down Syndrome (chromosomal error)
Phenylketonuria (PKU- defective recessive gene)
Klinefelter syndrome (sex-linked chromosomal abnormality)
Sickle-cell anemia (recessive gene)

31. Chromosomal Errors Most incompatible with survival
Variations in number sex chromosomes
Turner’s XO
Klinefelter’s XXY
XYY
Variations in number of other chromosomes
Down’s Syndrome, Trisomy 21
Edward’s Syndrome; Trisomy 17

33. PKU Recessive gene disorder
causes excessive buildup of phenylalaline causing brain damage
environmental intervention (diet) can reduce effects

34. Huntington’s Disease dominant gene disorder
50% chance of offspring inherit the disorder
1/15,000 incidence
charcterized by severe mental and physical disorder
lag in onset of symptoms (35-45 yrs) accounts for continued occurrence
can be detected through genetic testing

36. Biology and Culture
Cultural evolution can also account for existence of skills in a population
Innovations passed onto succeeding generations
Through processes of direct instruction, language, and demonstration
Little evidence of cultural evolution in other species
Meme: basic unit of cultural evolution

37. Cultural and Survival Some cultural tools may ensure survival
Hunting, gathering methods
Language
Child rearing practices (Quechuan babies)

38. Coevolution
Two forms of evolution (cultural and biological) influence each other
Evidence that culture has influenced biology through the impact it has on reproductive advantage (e.g., tool use)
The problems of sorting out the nature-nurture influence