Copyright © 2016, 2012, 2008 by Laura E. Berk. All Rights Reserved Infants, Children, and Adolescents Eighth Edition Chapter 2 Genetic and Environmental Foundations

Copyright © 2016 Laura E. Berk. All Rights Reserved Learning Objectives (Genetics and Environment) 1. What are genes, and how are they transmitted from one generation to the next? 2. Describe various patterns of genetic inheritance. 3. Describe major chromosomal abnormalities, and explain how they occur. 5. Explain the various ways heredity and environment may combine to influence complex traits.

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved Genetic Foundations Figure 2.2

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved Twins Fraternal/Dizygotic: two zygotes, or fertilized ova Identical/Monozygotic: one zygote that divides into two individuals

Copyright © 2016 Laura E. Berk. All Rights Reserved Maternal Factors Related to Fraternal Twinning Ethnicity Family history of twinning Age Nutrition Number of births Fertility drugs and in vitro fertilization

Copyright © 2016 Laura E. Berk. All Rights Reserved Patterns of Gene–Gene Interactions Alleles inherited from the parents are either dominant or recessive, determining: Physical traits Disabilities and diseases

Copyright © 2016 Laura E. Berk. All Rights Reserved Dominant–Recessive Inheritance Figure 2.3

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.

Copyright © 2016 Laura E. Berk. All Rights Reserved X-Linked Inheritance Figure 2.4

Copyright © 2016 Laura E. Berk. All Rights Reserved Genomic Imprinting and Mutation Imprinting 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.)

Copyright © 2016 Laura E. Berk. All Rights Reserved Sex Chromosomal Disorders DisorderDescriptionTreatment XYY syndromeAbove-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.

Copyright © 2016 Laura E. Berk. All Rights Reserved Reproductive Choices Genetic counseling helps couples assess risk of hereditary disorders and choose family goals accordingly. Options: Conception—knowing risks Reproductive technologies Adoption

Copyright © 2016 Laura E. Berk. All Rights Reserved Prenatal Diagnostic Methods Amniocentesis Chorionic villus sampling Fetoscopy Ultrasound Maternal blood analysis Preimplantation genetic diagnosis

Copyright © 2016 Laura E. Berk. All Rights Reserved Fetal Medicine Can result in complications, the most common being premature labor or miscarriage Surgery Blood transfusions Bone marrow transplants

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved 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

Copyright © 2016 Laura E. Berk. All Rights Reserved Gene–Environment Interaction Figure 2.9 (Based on Gottlieb, 2007)

Copyright © 2016 Laura E. Berk. All Rights Reserved Gene–Environment Correlation Passive correlation Evocative correlation Active correlation Niche-picking

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.

Copyright © 2016 Laura E. Berk. All Rights Reserved The Epigenetic Framework Figure 2.11

Copyright © 2016 Laura E. Berk. All Rights Reserved 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.