Ch. 2 Biological and Environmental Foundations and Prenatal Development

Chromosomes

rod-shaped structures that hold genes, the basic units of heredity.

Genes

units of heredity that carry instructions for traits.

DNA

complex molecule shaped like a twisted ladder that makes up genes.

Genome

the full set of genetic material; all humans share a genome but are genetically unique.

Mitosis

process by which DNA replicates to form new cells with identical genetic material.

Meiosis

process by which gametes (sex cells) reproduce.

Zygote

fertilized egg with 46 chromosomes (23 from each parent).

Sex Chromosomes

the 23rd pair of chromosomes that determine sex (XX or XY).

Dizygotic Twins (DZ)

fraternal twins; two eggs fertilized by different sperm.

Monozygotic Twins (MZ)

identical twins; one zygote splits into two genetically identical zygotes.

Dominant-Recessive Inheritance

dominant genes are always expressed; recessive genes expressed only when paired with another recessive.

Incomplete Dominance

both genes influence a trait (example: sickle cell trait).

Genomic Imprinting

gene expression depends on whether it is inherited from the mother or father (example: Prader-Willi or Angelman syndrome).

Polygenic Inheritance

traits influenced by multiple genes (example: intelligence, temperament).

PKU (Phenylketonuria)

a recessive disorder where the body cannot break down phenylalanine, leading to brain damage if untreated.

X-linked Disorders

disorders linked to the X chromosome (examples: Fragile X syndrome, hemophilia).

Down Syndrome

chromosomal abnormality with an extra 21st chromosome (trisomy 21).

Sex Chromosome Abnormalities

conditions such as Klinefelter syndrome and Turner syndrome.

Mutation

sudden change in gene structure; may involve one or many genes, can be harmful or beneficial.

Assisted Reproductive Technology (ART)

medical techniques to aid conception.

Artificial Insemination

sperm is injected into the uterus.

In Vitro Fertilization (IVF)

ova fertilized outside the body and implanted in uterus.

Surrogacy

another woman carries a baby for intended parents.

Phenotype

observable traits from interaction of genes and environment.

Behavior Genetics

study of how genes and environment shape traits and behaviors.

Heritability

extent to which variation in traits is due to genetics.

Twin Studies & Adoption Studies

methods to study genetic vs. environmental influence.

Range of Reaction

potential range of trait expression depending on environment.

Canalization

genetic restriction of development to one or few outcomes.

Gene-Environment Correlation

genetically influenced traits lead to environments that support them.

Epigenetics

environment influences which genes are expressed.

Germinal Period (0-2 weeks)

zygote divides, blastocyst forms, implantation in uterus occurs.

Blastocyst

fluid-filled sphere of cells that develops into embryo.

Implantation

blastocyst embeds into uterine wall.

Embryonic Period (3-8 weeks)

major structures form; ectoderm, endoderm, mesoderm layers develop.

Amnion

membrane with fluid that cushions and protects embryo.

Placenta

organ of exchange between mother and fetus.

Neural Tube

structure that becomes the central nervous system.

Fetal Period (9 weeks-birth)

rapid growth and brain development; coordinated movement; substantial weight gain in final 3 months.

Prenatal Diagnosis

medical tests including ultrasound, fetal MRI, amniocentesis, chorionic villus sampling (CVS), and noninvasive prenatal testing (NIPT).

Teratogen

harmful agent that disrupts prenatal development, causing birth defects.

Critical Periods

times when exposure to teratogens has the greatest impact (germinal and embryonic stages).

Dose Principle

higher exposure increases risk of harm.

Sleeper Effect

problems appear later from earlier teratogen exposure.

Fetal Alcohol Spectrum Disorders (FASD)

effects from prenatal alcohol exposure.

Other Teratogens

prescription/nonprescription drugs, tobacco, marijuana, cocaine, opioids.

Maternal Nutrition

2,200-2,900 calories daily; folic acid needed to prevent neural tube defects.

Spina Bifida

lower neural tube fails to close → paralysis.

Anencephaly

upper neural tube fails to close → death shortly after birth.

Maternal Illness

illnesses (HIV, Zika, etc.) can harm fetus.

Maternal Stress

severe, chronic stress affects fetal development, possibly via epigenetics.

Maternal Age

risks increase after age 35-40 (but most older mothers still have healthy infants).

Paternal Age

advanced paternal age linked to chromosomal abnormalities and disorders.

Prenatal Care

medical and educational services for pregnant women; barriers include lack of insurance, transport, and childcare.

Labor - Three Stages

dilation, delivery, and placenta separation.

Epidural

common anesthetic during childbirth.

Cesarean Section (C-section)

surgical delivery through abdomen.

Breech Position

baby positioned feet or bottom first.

Natural Childbirth

pain reduction via breathing/relaxation (Lamaze, doula support).

Home Birth

more common outside U.S.; often managed by midwives.

Apgar Scale

quick newborn health assessment at 1 and 5 minutes after birth.

Low Birthweight (LBW)

less than 5.5 lbs (2,500 g).

Very Low Birthweight (VLBW)

less than 3.5 lbs (1,500 g).

Extremely Low Birthweight (ELBW)

less than 1 lb 10 oz (750 g).

Preterm

born before due date.

Small for Date

full term but underweight from slow growth.

Kangaroo Care

skin-to-skin contact intervention for LBW infants.