1. Genetic and Environmental Foundations
Chapter 2
Genetic and Environmental Foundations

2. Physical attractiveness of premature infants affects outcome at discharge from the NICU Badr, LK & Abdallah, B (2001) Infant Behavior and Development, vol. 24, p. 129+

3. Genetic Foundations
Chromosomes – store and transmit genetic information.
Genes – segments of DNA located along the chromosomes
DNA – substance of which genes and chromosomes are made
less than two percent of a person's DNA represents active genes! The rest of the DNA seems to be involved mediating how the genes are expressed.
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4. Chromosomes, Cells, and Sex: Terminology
Autosomes
The 22 pairs of chromosomes that are not sex chromosomes
Sex Chromosomes
23rd pair of chromosomes
Determines sex
XX = female, XY = male
Gametes
Sex cells: sperm and ova
Zygote
Sperm and ovum united

5. Twins Fraternal/Dizygotic Identical/Monozygotic
two zygotes, or fertilized ova
Identical/Monozygotic
one zygote that divides into two individuals
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6. Alleles Two forms of the same gene
appear at the same place on both chromosomes in a pair
one inherited from each parent
homozygous—the two alleles are alike
heterozygous—the alleles differ

7. Genetic Principles
Homozygous: in a pair, both genes for a trait are the same
Eg:
Heterozygous: gene pair has 2 different gene types for a trait

8. III. Genetic Principles
Dominant inheritance: receive genes for contradictory traits; dominant trait is expressed (eg: )
Recessive Inheritance: homozygous trait, receives 2 of the same recessive genes for that trait (eg:

9. Examples of Dominant and Recessive Characteristics
Table 2.2
Source: McKusick, 2007.

10. Dominant-Recessive Inheritance need only 1 copy of gene to show disorder Huntington’s Disease: example of dominant inheritance gene on chromosome 4 identified in 1993
Dad: no disease (hh)
Mom: has disease (Hh)
Dad: h
Mom: H
Mom: h

11. PKU: recessive inheritance need 2 copies of recessive gene to show disease
Dad: carrier (Np)
Mom: carrier (Np)
Dad: N
Dad: p
Mom: N
Mom: p

12. X-Linked Inheritance
Figure 2.5

13. Sex-linked disorders carried on X chromosome

14. Color-blindness: sex linked

15. Mutation Somatic Mutation: Germline Mutation:
Normal body cells mutate, an event that can happen at any time in life.
The DNA defect can eventually become widespread enough to cause disease or disability.
Germline Mutation:
Takes place in the cells that give rise to gametes
Defective DNA is passed on to the next generation.

16. Chromosomal Abnormalities
Down syndrome
Trisomy 21
Sex chromosome abnormalities
Problems with the number of X or Y chromosomes
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17. Risk of Down Syndrome and All Chromosomal Abnormalities by Maternal Age
Figure 2.6

18. Prenatal Diagnostic Methods
Amniocentesis
Chorionic villus sampling
Fetoscopy
Ultrasound
Maternal blood analysis
Preimplantation genetic diagnosis (PGD)
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19. Karotype of DNA
Figure 2.1
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20. Genetic Principles
Polygenic Inheritance: many genes interact to affect a trait
(eg:  intelligence; skin color; athleticism)
Genotype: the complete set of genes (dominant and recessive) we’ve inherited from biological parents; present at conception
Phenotype: the outward expression of those genes; physical characteristics (expressed genes are influenced by pre and post-natal factors)

21. Twins Fraternal/Dizygotic – two zygotes, or fertilized ova
Identical/Monozygotic – one zygote that divides into two individuals
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22. Genetic Methods twin and adoption studies
Twin studies: are identical twins (MZ) more similar to each other than fraternal twins (DZ)?
MZ= monozygotic
DZ= dizygotic 
Did MZ pair share a placenta?

23. Placental arrangement in twins
a) Fraternal and some identical twins have separate placentas
b) Identical twins sharing a placenta (most MZ twins share 1 placenta)
Twin-to-twin transfusion syndrome (identical only)

24. Influences on Individual Differences
Heritability (h2): variation in a trait within a group attributable to genes
Shared Environment: common experiences
Non-shared Environment: unique experiences

25. Heritability of intelligence

26. Heritability of IQ

27. Heritability of schizophrenia

28. The Alternative of Adoption
Adopted children tend to have more learning and emotional difficulties than other children.
The child’s age at adoption correlates to learning and emotional difficulties experienced.
Most adopted children eventually fare well.

29. Environmental Contexts for Development
Family
Socioeconomic status
Neighborhoods
Towns and cities
Cultural context
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30. Socioeconomic Status and Family Functioning
Timing of family life cycle
Later parenthood (late 20s/early 30s)
Values and expectations
Father’s involvement
Communication and discipline styles
Children’s cognitive development

31. Affluence
Many affluent parents are not physically and emotionally available for their children.
These parents often make excessive demands for achievement.
Adolescents whose parents value achievement over character often have academic and emotional problems.

32. Poverty Emotional drain Joblessness High divorce rate Chronic stress
Parents < 25 with children hardest hit
Most homeless families consist of women with children under 5

33. Neighborhoods and Schools
Neighborhoods offer resources and social ties that play an important part in children’s development.
Higher-SES families are less dependent on their immediate surroundings than are low-SES families.
Social ties linking families together break down in areas with unemployment, crime, and population turnover.
Children spend an average of 14,000 hours in school by high school graduation.
Parent–school contact supports development at all ages.

34. The Cultural Context Culture shapes every aspect of daily life.
Different cultures have different values; North American culture values the independence, self-reliance, and privacy of the family.
Subcultures
Extended-family households
Stay-at-home dad movement
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35. The African-American Extended Family
Today, more black than white adults have relatives other than their own children living in the same household.
The extended-family system provides emotional support and the sharing of resources, and helps reduce the stress of poverty and single parenthood.
These arrangements also place a high value on cooperation and moral and religious values.

36. Individualist and Collectivist Societies

37. Reaction Range
Figure 2.9

38. V. Genotype-Environment Correlation
 1.       Passive Gene-Environment
Parents who are genetically related to child provide rearing environment
2.       Evocative (eg: attractive infant study)
Child’s genotype elicits certain environments
3.       Active (niche-picking)
Seek out environments that are compatible/stimulating to your predisposition
VIDEO: Good example of gene-environment interaction

39. The Epigenetic Framework
Epigenetics: environmental influences alter gene expression; bidirectional exchange between heredity and environment (cellular and social)
eg: ADHD (prenatal exposure changes expression of DD genotype on chromosome 12)