Genetic and Environmental Foundations Chapter 2 Genetic and Environmental Foundations

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+

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. © Noiral | Dreamstime.com

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

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

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

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  

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:  

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

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

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

X-Linked Inheritance Figure 2.5

Sex-linked disorders carried on X chromosome

Color-blindness: sex linked

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.

Chromosomal Abnormalities Down syndrome Trisomy 21 Sex chromosome abnormalities Problems with the number of X or Y chromosomes © Jscreationzs | Dreamstime.com

Risk of Down Syndrome and All Chromosomal Abnormalities by Maternal Age Figure 2.6

Prenatal Diagnostic Methods Amniocentesis Chorionic villus sampling Fetoscopy Ultrasound Maternal blood analysis Preimplantation genetic diagnosis (PGD) © John Keith | Dreamstime.com

Karotype of DNA Figure 2.1 Copyright © 2010 Pearson Education, Inc. All Rights Reserved.

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)

Twins Fraternal/Dizygotic – two zygotes, or fertilized ova Identical/Monozygotic – one zygote that divides into two individuals © Stephanie Swartz | Dreamstime.com

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?

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)

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

Heritability of intelligence

Heritability of IQ

Heritability of schizophrenia

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.

Environmental Contexts for Development Family Socioeconomic status Neighborhoods Towns and cities Cultural context © Murali Nath | Dreamstime.com

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

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.

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

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.

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 © Camille Bruggner | Dreamstime.com

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.

Individualist and Collectivist Societies

Reaction Range Figure 2.9

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

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)