1. Infants, Children, and Adolescents
Eighth Edition
Chapter 2
Genetic and Environmental Foundations

2. Learning Objectives (1 of 2)
2.1 What are genes, and how are they transmitted from one generation to the next?
2.2 Describe various patterns of genetic inheritance.
2.3 Describe major chromosomal abnormalities, and explain how they occur.
2.4 What procedures can assist prospective parents in having healthy children?

3. Learning Objectives (2 of 2)
2.5 Describe family functioning from the perspective of ecological systems theory, along with aspects of the environment that support family well-being and children’s development.
2.6 Explain the various ways heredity and environment may combine to influence complex traits.

4. 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 up of

5. Genetic Foundations
Figure 2.2: DNA’s ladderlike structure
Figure 2.2

6. Meiosis Process of cell division used to create gametes (sex cells)
Halves the number of chromosomes normally present
When sperm and ovum unite, zygote will have 46 chromosomes again.
Ensures transmission of a constant quantity of genetic material

7. Twins Fraternal/Dizygotic: two zygotes, or fertilized ova
Identical/Monozygotic: one zygote that divides into two individuals

8. Maternal Factors Related to Fraternal Twinning
Ethnicity
Family history of twinning
Age
Nutrition
Number of births
Fertility drugs and in vitro fertilization

9. Patterns of Gene–Gene Interactions
Alleles inherited from the parents are either dominant or recessive, determining:
Physical traits
Disabilities and diseases

10. Dominant–Recessive Inheritance
Figure 2.3: Dominant-recessive mode of inheritance, as illustrated by PKU
Figure 2.3

11. X-Linked Inheritance A harmful allele is carried on the X chromosome.
Males are more likely to be affected.
Nature compensates: Worldwide, about 106 boys are born for every 100 girls.

12. X-Linked Inheritance
Figure 2.4: X-linked inheritance
Figure 2.4

13. Genomic Imprinting and Mutation
Chemical marker that activates either father’s or mother’s gene
Often temporary
Mutation
Sudden, permanent change in a DNA segment
Can occur spontaneously or be caused by hazardous environmental agents

14. Mutation Somatic 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.

15. Chromosomal Abnormalities
Down syndrome
Results from problems with the 21st pair of chromosomes
Sex chromosome abnormalities
Results from problems with the X or Y chromosomes

16. Down Syndrome
95% of cases result from failure of 21st chromosome pair to separate during meiosis.
Consequences include:
Intellectual disability
Speech problems and limited vocabulary
Slow motor development
Distinct physical features
Increased risk of Alzheimer’s disease starting around age 40

17. Risk of Down Syndrome and All Chromosomal Abnormalities by Maternal Age
Figure 2.5: Risk of Down syndrome and all chromosomal abnormalities by maternal age
Figure 2.5
(From R. L. Schonberg & C. J. Tifft, 2012, “Birth Defects and Prenatal Diagnosis,” from Children with Disabilities, 7/e, M. L. Matshaw, N. J. Roizen, & G. R. Lotrecchiano, editors, p. 50. Baltimore: Paul H. Brookes Publishing Co, Inc. Adapted by permission.)

18. Sex Chromosomal Disorders
Description
Treatment
XYY syndrome
Above-average height; large teeth. Normal intelligence and sexual development.
No special treatment necessary.
Triple X syndrome (XXX)
Tall. Impaired verbal intelligence. Normal sexual development.
Special education for verbal ability problems.
Klinefelter syndrome (XXY)
Tall; feminine body-fat distribution. Impaired verbal intelligence. Incomplete sexual development.
Hormone therapy to stimulate sexual development; special education for verbal ability problems.
Turner syndrome (XO)
Short stature; webbed neck. Impaired spatial intelligence. Incomplete sexual development.
Hormone therapy to stimulate physical growth and sexual development; special education for spatial ability problems.

19. Reproductive Choices
Genetic counseling helps couples assess risk of hereditary disorders and choose family goals accordingly.
Options:
Conception—knowing risks
Reproductive technologies
Adoption

20. Prenatal Diagnostic Methods
Amniocentesis
Chorionic villus sampling
Fetoscopy
Ultrasound
Maternal blood analysis
Preimplantation genetic diagnosis

21. Fetal Medicine
Can result in complications, the most common being premature labor or miscarriage
Surgery
Blood transfusions
Bone marrow transplants

22. Genetic Engineering Human Genome Project
Researchers have mapped the sequence of all human DNA base pairs.
Working on identifying all genes and their functions
Thousands of genes are already identified, including those involved in disorders of the heart, digestive system, blood, eye, and nervous system, and many forms of cancer.
New treatments under development include gene therapy and proteomics.

23. Adoption
Adopted children show more learning and emotional difficulties:
Early stress and conflict-ridden relationships
Children and adoptive parents less alike in intelligence and personality
Age at adoption can influence difficulties.
With sensitive caregiving, most children ultimately fare well.

24. Reproductive Technologies
Donor insemination and in vitro fertilization
Ethical concerns: post-menopausal childbearing, “designer babies”
Surrogate motherhood
Ethical concerns: Exploitation of financially needy women, insecurity of surrogate’s own children

25. Environmental Contexts for Development
Family
Socioeconomic status
Affluence/poverty
Neighborhoods
Schools
Cultural context

26. Family Influences on Development
Direct
Two-person relationships
Indirect
Third parties
Adapting to Change
Changes from within and outside the family

27. Socioeconomic Status and Family Functioning
Timing of parenthood and family size
Values and expectations
Communication and discipline styles
Children’s cognitive development

28. Worldwide Education of Girls
Most children not enrolled in school are poverty- stricken girls.
Educating girls improves:
Children’s cognitive and literacy development
Family health
Mother–child interactions

29. Worldwide Education of Girls (continued)
The UN reports that educating girls is the most effective means of combating:
Poverty
Maternal and child mortality
Disease
Gender inequality
Economic and social instability

30. Affluence Affluent parents:
Often physically and emotionally unavailable
Make excessive demands for achievement
Affluent children:
Poor academic achievement
Alcohol and drug use
High levels of anxiety and depression
Eating meals with parents can reduce children’s adjustment difficulties.

31. Poverty 22% (14.5 million) U.S. children live in poverty
Rates increase among ethnic minorities
More likely to suffer from:
Lifelong poor health
Poor academic achievement
Mental illness
Impulsivity, aggression, antisocial behavior
Homelessness

32. Neighborhoods
After-school programs and clubs are important to low-SES children.
Increased self-confidence
Better school achievement
Attendance at neighborhood programs is often hindered by violence.
Family–neighborhood ties help parents.
Parental self-worth
Parental access to information and services
Child-rearing support

33. Schools Parent–school contact is important at all ages.
High-SES parents are more likely to be involved.
Low-SES and ethnic minority parents may feel uncomfortable or have less time.

34. The Cultural Context Culture shapes every aspect of daily life.
Cultures vary in values; U.S. culture emphasizes independence, self-reliance, and privacy of the family.
Subcultures, including ethnic minority groups, often have cooperative family structures

35. The African-American Extended Family
Benefits of the African-American extended family:
Helps reduce the stress of poverty and single parenthood
Family members help with child rearing.
Adolescent mothers are more likely to finish high school and get a job.
Transmits African-American culture

36. Individualism versus Collectivism
People concerned with own personal goals
Value independence
Collectivism
People concerned with group goals over individual goals
Value interdependence

37. U.S. Public Policy Shortcomings
Children without health insurance
Substandard child care
Weak enforcement of child support payments
Poor vocational preparation for non-college- bound youths
High school dropouts

38. Efforts to Improve Children’s Condition
1989 Convention on the Rights of the Child (UN General Assembly)
Influential interest groups
Children’s Defense Fund
National Center for Children in Poverty

39. Heritability Estimates
Measure the extent to which individual differences in complex traits are due to heredity
Obtained from kinship studies
Estimates range from 0 to 1.00
Limitations:
Accuracy depends on genetic and environmental variation in the population
Can be misapplied
Limited usefulness

40. Gene–Environment Interaction
Figure 2.9: Gene-environment interaction, illustrated for intelligence by three children who differ in responsiveness to quality of the environment
Figure 2.9
(Based on Gottlieb, 2007)

41. Gene–Environment Correlation
Passive correlation
Evocative correlation
Active correlation
Niche-picking

42. Environmental Influences on Gene Expression
Gene–environment correlation is viewed as driven by genetics.
Many researchers take issue with the supremacy of heredity.
Bidirectional influences between heredity and environment
Adults can uncouple unfavorable gene– environment correlations.

43. The Epigenetic Framework
Figure 2.11: Epigenesis
Figure 2.11

44. Smoking During Pregnancy Alters Gene Expression
Maternal smoking and ADHD
Prenatal tobacco exposure influences a chromosome-5 (DD) genotype.
In animal research, tobacco smoke stimulates the DD genotype to release chemicals that promote impulsivity and overactivity.
Smoking alters expression of the DD genotype.

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