Chapter_3_-_3rd_edition_-_st

Chapter Overview

• Title: Child Development: A Cultural Approach Third Edition

• Focus: Genetics and Prenatal Development

Genetic Basics

Key Terms

• Genotype: Total genetic makeup of an individual.

• Phenotype: Observable traits or characteristics influenced by genotype and environment.

• Sex Chromosomes: 23rd pair of chromosomes determining biological sex (XX for females, XY for males).

Human Genetics

Chromosomes

• Humans have 46 chromosomes (23 pairs).

• Chromosomes are made of DNA, which stores genetic information organized into genes.

• Genome: The complete set of hereditary genetic information.

DNA Structure

• DNA consists of nucleotide pairs.

Genotype vs. Phenotype

Differences

• Genotype influences phenotype, which is also shaped by the environment.

• Dominant vs. Recessive Genes: Dominant genes mask the effects of recessive genes. Incomplete dominance can occur when heterozygous for alleles.

Traits and Inheritance Patterns

Inheritance Examples

• Dominant Traits: Curly hair, dark hair, freckles.

• Recessive Traits: Straight hair, blonde hair, attached earlobes.

Incomplete Dominance

• E.g., Sickle-cell trait and malaria resistance; one recessive gene leads to sickle-cell trait without anemia.

• Polygenic Inheritance: Traits influenced by multiple genes.

Sex Chromosomes

Importance

• XX (female) and XY (male) chromosomes determine sex.

• Males are more susceptible to X-linked recessive disorders (e.g., hemophilia).

Gene-Environment Interactions

Behavioral Genetics

• Studies focus on the influence of genetics vs. environment on development.

• Use of twin studies to parse out genetic and environmental impacts (Monozygotic vs. Dizygotic).

Heritability

• Heritability: Proportional influence of genetics on differences in individuals within a population.

• Concordance Rates: Measurement of similarity in phenotypes among family members.

Epigenetics

Definitions

• Epigenetics: Interactions between genes and environmental influences.

• Reaction Range: Genetic potential established by genes, modified by environmental context.

Theory of Genotype-Environment Effects

Forms of Interaction

• Passive: Parents provide both genes and environment.

• Evocative: Genetic traits elicit reactions from the environment.

• Active: Individuals select environments that match their genetic predispositions.

Prenatal Development

Phases

• Germinal Period: First two weeks; implantation process.

• Embryonic Period: Weeks 3-8; formation of major organs and systems from embryonic layers.

• Fetal Period: Week 9 to birth; significant growth and development.

Milestones

• Germinal Period: Formation of blastocyst, implantation.

• Embryonic Period: Development of ectoderm (nervous system), mesoderm (muscles, bones), endoderm (digestive system).

• Fetal Period: Genitalia development, responsiveness to external stimuli.

Prenatal Care

Cultural Variations

• Traditional Cultures: Focus on ancestral practices with limited medical oversight.

• Developed Countries: Scientific approaches with emphasis on nutrition, exercise, and avoiding teratogens.

Teratogens

Overview

• Substances causing developmental harm (malnutrition, drugs, alcohol).

• Critical influence during the embryonic stage.

Major Teratogens

• Malnutrition: Leads to severe developmental issues, especially lack of folic acid.

• Infectious Diseases: Rubella and AIDS pose significant risks.

• Alcohol and Drugs: Can result in fetal alcohol spectrum disorders and other complications.

• Tobacco: Linked to low birth weight and developmental issues.

Chromosomal Disorders

Causes

• Arise from errors during meiosis leading to too many or too few chromosomes.

• Common chromosomal disorders include Down syndrome and disorders related to sex chromosomes, which can impact reproductive health and cognition.

Prenatal Testing and Counseling

Techniques

• Ultrasounds: Imaging technology for monitoring fetal development.

• Amniocentesis and Chorionic Villus Sampling: Tests involving fetal cells to identify genetic conditions.

Genetic Counseling

• Recommended for couples with a history of genetic disorders or advanced parental age.

Infertility

Definition

• Inability to conceive after one year of unprotected intercourse.

Psychological and Social Implications

• Varies by culture; can lead to emotional distress and social stigma, especially for women.

Causes and Treatments

• Male factors: Low sperm count and quality; female factors: ovulation problems, age-related decline.

• Treatments often involve assisted reproductive technologies (ART) such as IVF and fertility drugs.