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

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?

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.

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

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

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

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

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

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

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

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.

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

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

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.

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

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

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.)

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.

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

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

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

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.

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.

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

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

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

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

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

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

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.

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

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

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.

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

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

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

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

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

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

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)

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

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.

The Epigenetic Framework Figure 2.11: Epigenesis Figure 2.11

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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