03 – Prenatal Development and Childbirth

Fertilization

Marks the beginning of development where the sperm and ovum combine to create a zygote in the fallopian tube.

Fertile Window

Unpredictable time during which conception is possible.

Menarche

Onset of menstruation in females, marking sexual maturity.

Nocturnal Emission

Involuntary ejaculation during sleep in males, marking sexual maturity.

Ovulation

Rupture of a mature follicle, occurring about every 28 days until menopause.

Zygote

Fertilized egg that duplicates through cell division to produce all the baby’s cells.

Unsuccessful Fertilization

Leads to the death of gametes—sperm absorbed by white blood cells, ovum exits via the vagina.

Dizygotic Twins

Fraternal twins from two different eggs fertilized by two sperm.

Monozygotic Twins

Identical twins from a single fertilized egg that splits.

Twin-to-Twin Transfusion Syndrome

Condition where nutrients are unequally shared due to abnormal placenta blood vessels.

Mitosis

Division of somatic cells creating two identical diploid daughter cells.

Meiosis

Cell division forming four non-identical haploid gametes, introducing genetic variation.

Gene

Segment of DNA carrying instructions for organism development and maintenance.

Chromosomes

23 pairs of threadlike DNA-containing structures.

DNA (Deoxyribonucleic Acid)

Molecule with genetic instructions for life.

Mutation

Permanent alteration in a DNA sequence due to replication errors, mutagens, or viruses.

Protein

Building blocks of cells and body process regulators.

Human Genome

Map showing location of all human genes.

Methylation

Atoms attaching to genes, switching them on or off.

Susceptibility Genes

Genes increasing risk of disease or aging.

Longevity Genes

Genes decreasing disease risk and increasing lifespan.

Sex Chromosomes

XX for females, XY for males; determine biological sex.

Autosomes

Chromosomes not involved in sex determination.

X-linked Inheritance

Mutated gene on X chromosome more commonly affects males.

Mendelian Genetics

Trait inheritance rules including dominance, segregation, and independent assortment.

Allele

Variants of a gene at the same locus on paired chromosomes.

Homozygous

Having identical alleles for a trait.

Heterozygous

Having different alleles for a trait.

Dominant Inheritance

Trait expressed when one dominant allele is present.

Recessive Inheritance

Trait expressed only when both alleles are recessive.

Polygenic Inheritance

Traits controlled by multiple genes with additive effects.

Multifactorial Transmission

Trait expression modified by environmental experiences.

Genotype

Genetic heritage; the actual gene sequence.

Phenotype

Observable traits influenced by genes and environment.

Epigenesis

Mechanism that turns genes on/off depending on need or environment.

Genetic Imprinting

Expression of a gene differs based on maternal or paternal origin.

Down Syndrome

Trisomy 21; intellectual disability, facial features, health risks.

Cri-du-chat Syndrome

Deletion on chromosome 5; cat-like cry, intellectual disability.

Edwards Syndrome

Trisomy 18; severe disability, heart defects.

Patau Syndrome

Trisomy 13; severe abnormalities, cleft lip/palate.

Prader-Willi Syndrome

Missing/inactive paternal genes on chromosome 15; obesity, intellectual disability.

Alpha Antitrypsin Deficiency

Mutation on chromosome 14; liver/lung disease.

Alpha Thalassemia

Chromosome 16 mutation; severe anemia, often fatal at birth.

Beta Thalassemia (Cooley’s Anemia)

Chromosome 11 mutation; severe anemia, often fatal by young adulthood.

Cystic Fibrosis

Chromosome 7 mutation; mucus buildup in lungs and digestive system.

Anencephaly

Failure of neural tube closure; absence of major brain regions.

Spina Bifida

Chromosome 11 mutation; neural tube defect causing physical and mental issues.

Phenylketonuria (PKU)

Inability to metabolize phenylalanine; leads to intellectual disability if untreated.

Polycystic Kidney Disease

Kidney enlargement; respiratory or heart failure (infantile), kidney problems (adult).

Sickle-Cell Anemia

Recessive gene causes misshapen red blood cells; low oxygen transport.

Tay-Sachs Disease

Lipid accumulation in brain; developmental regression.

Diabetes

Insulin deficiency or resistance affecting sugar metabolism.

Huntington’s Disease

Degeneration of CNS; muscle and mental decline.

Angelman Syndrome

Maternal gene absence on chromosome 15; delays, seizures, happy demeanor.

Turner Syndrome (XO)

Female missing second X; short stature, infertility.

Klinefelter Syndrome (XXY)

Male with extra X; gynecomastia, infertility.

Triple X Syndrome (XXX)

Extra X in females; learning disabilities, mild symptoms.

XYY Syndrome

Male with extra Y; tall, low verbal IQ.

Fragile X Syndrome

Expansion on X chromosome; developmental delays.

Duchenne Muscular Dystrophy

X-linked mutation; fatal muscle weakness in males.

Behavior Genetics

Study of heredity/environment on development and traits.

Heritability

Percentage of trait variance due to genes.

Concordance

Degree to which twins share traits.

Twin Study

Compares identical vs. fraternal twin similarity.

Adoption Study

Compares traits of adopted children to biological vs. adoptive parents.

Reaction Range

Genotype sets potential range; environment determines where within it.

Canalization

Traits strongly determined by genes, minimally influenced by environment.

Genotype-Environment Interaction

Different responses to same environment due to genetic differences.

Genotype-Environment Correlations

Genes influence the type of environment one experiences.

Passive Correlation

Parents provide genes and environment.

Evocative Correlation

Child’s traits elicit specific environmental responses.

Active Correlation

Child seeks compatible environments (niche-picking).

Nonshared Environment

Unique influences affecting individual siblings differently.

Traits Affected

Obesity, Intelligence, Temperament, Personality, Schizophrenia.

Prenatal Development

Period from conception to birth, includes germinal, embryonic, and fetal stages.

Gestation

Time between conception and birth.

Gestational Age

Fetal age based on mother’s last menstrual cycle.

Cephalocaudal Principle

Development proceeds from head downward.

Proximodistal Principle

Development proceeds from center of the body outward.

Germinal Period (fertilization to 2 weeks)

Stage of prenatal development from fertilization to 2 weeks when rapid cell division occurs and implantation begins.

Ectoderm

Outermost layer of embryonic cells which will become the nervous system and brain, sensory receptors, and skin parts.

Life-support systems for the embryo

Structures such as the amnion, umbilical cord, and placenta that develop rapidly to support the embryo.

Amnion

Sac that contains a clear fluid to protect and provide a controlled environment for the fetus.

Umbilical Cord

Connects the baby to the placenta, allowing exchange of nutrients and wastes.

Zygote cell division timeline

At 36 hours after fertilization, rapid mitosis begins; by the 3rd day, 16 to 32 cells; by the 4th day, 32 to 128 cells forming a blastocyst.

Blastocyst

Fluid-filled sphere of cells that floats freely in the uterus before implantation.

Embryonic Disk

Thickened cell mass from which the embryo begins to develop.

Implantation

Attachment of the blastocyst to the uterine wall, beginning around day 6 to 7 post-fertilization.

Amniotic Sac

Fluid-filled membrane that encases the developing embryo.

Placenta

Organ that allows oxygen, nourishment, and waste to pass between mother and embryo.

Embryonic Stage (2 to 8 weeks)

Period when the blastocyst is now called an embryo and organogenesis occurs rapidly.

Endoderm

Inner cell layer that develops into the digestive and respiratory systems.

Mesoderm

Middle cell layer that becomes circulatory system, bones, muscles, excretory and reproductive systems.

Organogenesis

Rapid development of organs and major body systems during the embryonic stage.

Critical Period

Time when the embryo is most vulnerable to harmful environmental influences.

Spontaneous Abortion

Natural miscarriage occurring often in the first trimester.

Stillbirth

Miscarriage occurring after 20 weeks of gestation.

Neural tube formation

Occurs around 3rd week, eventually becoming the spinal cord.

Key embryonic developments timeline

Eyes appear at 21 days, heart cells differentiate at 24 days, urogenital system at 4 weeks, arm and leg buds emerge, heart chambers form, blood vessels appear.

Fetal Stage (8 weeks to birth)

Stage starting at 8 weeks marked by rapid growth and increasing organ complexity.