Infants Children and Adolescents Eighth Edition Chapter 2

Infants, Children, and Adolescents Eighth Edition Chapter 2 Genetic and Environmental Foundations Copyright © 2016, 2012, 2008 by 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 21 st 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 21 st 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 Disorder Description XYY syndrome Above-average height; large teeth. Normal intelligence and sexual development. Triple X Tall. Impaired verbal syndrome (XXX) intelligence. Normal sexual development. Klinefelter Tall; feminine body-fat syndrome (XXY) distribution. Impaired verbal intelligence. Incomplete sexual development. Turner syndrome Short stature; webbed neck. (XO) Impaired spatial intelligence. Incomplete sexual development. Copyright © 2016 Laura E. Berk. All Rights Reserved Treatment No special treatment necessary. Special education for verbal ability problems. Hormone therapy to stimulate sexual development; special education for verbal ability problems. 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 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 povertystricken 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. Copyright © 2016 Laura E. Berk. All Rights Reserved