Human Development: Key Terms and Definitions

Flashcards on Human Development Key Terms and Definitions

Chromosomes

Threadlike structures made up of DNA that contain genes; humans typically have 46 (23 pairs).

Autosomes

The 22 pairs of chromosomes that are not sex chromosomes.

Sex chromosomes

The 23rd pair of chromosomes that determine the biological sex (XX for females, XY for males).

Deoxyribonucleic acid (DNA)

The chemical substance that makes up chromosomes and contains the genetic instructions for development and functioning.

Gene

A segment of DNA that codes for a specific trait or function.

Genotype

A person's complete set of inherited genes.

Phenotype

The observable characteristics resulting from the interaction of a person's genotype and environment.

Alleles

Alternative forms of the same gene.

Homozygous

Having two identical alleles for a given gene.

Heterozygous

Having two different alleles for a given gene.

Dominant

An allele that expresses its trait even if only one copy is present.

Recessive

An allele that is only expressed when two copies are present.

Incomplete dominance

A genetic situation in which neither allele is completely dominant, resulting in a blend of traits.

Sickle-cell trait

A genetic condition in which a person inherits one sickle-cell gene and one normal gene, often without symptoms.

Phenylketonuria (PKU)

A genetic disorder where individuals cannot metabolize phenylalanine, leading to brain damage if untreated.

Behavioral genetics

The study of the inheritance of behavioral and psychological traits.

Polygenic inheritance

The effect of multiple genes on a single trait.

Monozygotic twins

Identical twins formed from one zygote that splits into two embryos.

Dizygotic twins

Fraternal twins formed from two different eggs fertilized by two different sperm.

Niche-picking

The process of deliberately seeking environments that fit one's heredity.

Nonshared environmental influences

Aspects of the environment that differ among individuals, even in the same family.

Prenatal development

The process of growth and development within the womb, from conception to birth.

Zygote

A fertilized egg resulting from the union of sperm and egg.

In vitro fertilization

A reproductive technology where eggs are fertilized outside the body and then implanted into the uterus.

Implantation

The process by which the zygote attaches to the wall of the uterus.

Germ disc

A small cluster of cells near the center of the zygote that will develop into the baby.

Placenta

The structure through which nutrients and wastes are exchanged between the mother and fetus.

Embryo

The developing organism from the 3rd to 8th week after conception.

Ectoderm

The outer layer of the embryo, which becomes the skin, hair, and nervous system.

Mesoderm

The middle layer of the embryo, which forms muscles, bones, and the circulatory system.

Endoderm

The inner layer of the embryo, which becomes the digestive system and lungs.

Amnion

A sac that surrounds the embryo and is filled with amniotic fluid.

Amniotic fluid

The fluid surrounding the embryo that cushions and protects it.

Umbilical cord

The structure that connects the embryo to the placenta.

Cephalocaudal principle

The principle that growth occurs from the head downward.

Proximodistal principle

The principle that growth occurs from the center of the body outward.

Period of the fetus

The longest period of prenatal development, from the 9th week until birth.

Cerebral cortex

The outer layer of the brain involved in thinking, consciousness, and voluntary movement.

Vernix

A white, waxy substance that protects the fetus's skin.

Age of viability

The age (around 22-28 weeks) at which a fetus can survive outside the womb.

Spina bifida

A neural tube defect where the spinal cord does not develop properly.

Stress

A physical or psychological response to demands or challenges; excessive maternal stress can affect fetal development.

Teratogen

Any agent that can cause harm to a developing fetus.

Fetal alcohol spectrum disorder (FASD)

A range of physical, cognitive, and behavioral problems caused by prenatal alcohol exposure.

Ultrasound

A prenatal imaging technique using sound waves to create an image of the fetus.

Amniocentesis

A prenatal test that samples amniotic fluid to detect genetic abnormalities.

Chorionic villus sampling (CVS)

A prenatal test that samples tissue from the placenta to detect genetic conditions.

Non-invasive prenatal testing (NIPT)

A blood test that analyzes fetal DNA to screen for chromosomal conditions.

Fetal therapy

Medical treatment provided to the fetus while still in the womb.

Crowning

The stage in childbirth when the baby's head begins to emerge from the birth canal.

Hypoxia

A condition in which the baby does not get enough oxygen during birth.

Cesarean section (C-section)

A surgical method of delivering a baby through incisions in the abdomen and uterus.

Preterm or premature

A baby born before 37 weeks of gestation.

Low birth weight

A newborn weighing less than 5.5 pounds (2,500 grams).

Very low birth weight

A newborn weighing less than 3.3 pounds (1,500 grams).

Extremely low birth weight

A newborn weighing less than 2.2 pounds (1,000 grams).

Infant mortality

The death of an infant before the first birthday.