Human Development Through Lifespan: Chapter 2 – Beginning of Life and Prenatal Development (Vocabulary)

Vocabulary flashcards covering key terms related to the beginning of life, genetics, prenatal development, infertility, and prenatal testing.

Gametes

Reproductive cells: sperm in males and ovum (egg) in females; carry genetic material for reproduction.

Fertilization

Union of sperm and ovum that forms a zygote; marks the creation of a new genetic life.

Zygote

Single cell formed when a sperm fertilizes an ovum; contains about 25,000 genes on 46 chromosomes (23 pairs).

Chromosomes

Structures containing DNA; humans have 46 chromosomes arranged in 23 pairs.

Genes

Units of heredity located on chromosomes that guide development and traits.

Blastocyst

Early embryo stage around day 5 after fertilization, developing a hollow ball that implants in the uterus.

Monozygotic Twins

Twins from a single zygote that splits; genetically identical.

Dizygotic Twins

Twins from two separate ova fertilized by separate sperm; not genetically identical.

Sex Determination

At conception, the sperm’s 23rd chromosome (X or Y) determines the child’s sex; ovum always contributes an X.

X Chromosome

One of the two sex chromosomes; carries many genes and is present in both sexes.

Y Chromosome

The sex chromosome in males that determines male development when present with an X.

Genotype

The complete set of genetic information an individual carries.

Phenotype

Observable traits and characteristics resulting from genotype and environment.

Homozygous Alleles

Same alleles from both parents; e.g., blue-eyed allele from both sides.

Heterozygous Alleles

Different alleles from each parent; may express a dominant trait over a recessive one.

Dominant Allele

Allele that will be expressed if present in the genotype.

Recessive Allele

Allele that is expressed only when paired with another recessive allele.

Polygenic Inheritance

Traits determined by more than one gene (e.g., height, eye color complexity).

Reaction Range

Genetic potential for a trait expressed differently depending on environmental factors.

Blood Types (ABO)

Not purely dominant/recessive; combinations of A and B alleles can produce AB, A, B, or O phenotypes.

X-Linked Genes

Recessive genes on the X chromosome; males are at higher risk for X-linked disorders.

Red-Green Color Blindness

Common X-linked disorder where color perception is impaired.

Hemophilia

X-linked disorder affecting blood clotting; higher risk in males.

Genetic Disorders

Conditions caused by genetic factors, gene damage, environmental factors, or spontaneous mutation.

Genetic Counseling

Professional guidance to understand risks and implications of inherited disorders.

Prenatal Testing

Tests during pregnancy to assess fetal health and detect genetic issues.

Amniocentesis

Tests amniotic fluid (15–20 weeks) via needle; high accuracy for detecting defects; small miscarriage risk.

Ultrasound Sonography

Imaging using high-frequency sound waves to view the fetus; transvaginal ultrasound common in the first trimester.

Sonoembryology

Transvaginal ultrasound used in early pregnancy to examine fetal development.

Chorionic Villus Sampling (CVS)

Tests placental tissue (abdomen or cervix) for genetic abnormalities; slightly higher miscarriage risk than amniocentesis.

Multifactorial Transmission

Traits influenced by both genetics and environment; genotype sets potential range, phenotype realized within it.

Germinal Stage

Fertilization to 2 weeks; zygote divides, implants, placenta begins.

Embryonic Stage

2–8 weeks; development of ectoderm, endoderm, and mesoderm.

Ectoderm

Outer germ layer: becomes skin, hair, teeth, sense organs, brain, spinal cord.

Endoderm

Inner germ layer: becomes digestive system, liver, pancreas, respiratory system.

Mesoderm

Middle germ layer: becomes muscles, bones, blood, circulatory system.

Fetal Stage

8 weeks to birth; rapid growth, brain development, organ function; movement felt ~4 months; fetus can hear.

Infertility

Inability to conceive after 12–18 months; affects ~6% of couples; age-related decline.

ART (Assisted Reproductive Technology)

Medical techniques used to help achieve pregnancy (e.g., IVF, IUI).

Artificial Insemination / IUI

Sperm placed directly into the female reproductive tract by a clinician.

IVF (In Vitro Fertilization)

Ova are fertilized by sperm outside the body in a laboratory setting.

ICSI (Intracytoplasmic Sperm Injection)

IVF technique where a single sperm is injected directly into an egg.

Miscarriage

Spontaneous loss of pregnancy (spontaneous abortion); 15–20% of pregnancies end this way, often due to genetic issues.

Abortion

Voluntary termination of a pregnancy.

Teratogens

Environmental agents that can cause birth defects or developmental abnormalities; effects depend on timing and exposure.

Maternal Factors

Maternal diet, age, health, and support influencing prenatal development and outcomes.

Paternal Prenatal Influence

Less understood; potential genetic contributions from the father to fetal development.