Biological Inheritance

heredity

The biological transmission of characteristics from one generation to the next.

gene

The segments on a DNA molecule that act as hereditary blueprints for the organism’s development.

genotype

The genetic endowment of an individual.

phenotype

An organism’s observable characteristics that result from the interaction of the genotype with the environment.

natural selection

The process through which species survive and evolve, focusing on individuals with adaptive phenotypes.

chromosome

A threadlike structure made up of genes; humans have 46 chromosomes in every cell except sperm and ova.

DNA (deoxyribonucleic acid)

A long, double-stranded molecule that makes up chromosomes.

zygote

The single cell formed at conception from the union of the sperm and the ovum.

germ cells

Sperm and ova, specialized for sexual reproduction with half the chromosomes normal for a species.

somatic cells

All the cells in the body except the germ cells (ova and sperm).

mitosis

The process of cell duplication and division generating all of an individual’s cells except sperm and ova.

meiosis

The process that produces sperm and ova, each containing half of the parent cell’s original 46 chromosomes.

monozygotic (MZ) twins

Twins from one zygote with identical genotypes.

dizygotic (DZ) twins

Twins from two zygotes.

allele

The specific form of a gene influencing a particular trait.

homozygous

Having inherited two genes of the same allelic form for a trait.

heterozygous

Having inherited two genes of different allelic forms for a trait.

dominant allele

The allele expressed when an individual possesses two different alleles for the same trait.

recessive allele

The allele not expressed when an individual possesses two different alleles for the same trait.

carriers

Individuals who are heterozygous for a trait with a dominant and recessive allele.

mutation

An alteration in the molecular structure of an individual’s DNA.

gene pool

The total variety of genetic information possessed by a sexually reproducing population.

preconception tests

Analysis of parents’ DNA to determine the risk of genetic disorders in offspring.

prenatal tests

Tests to analyze an embryo or fetus's DNA for genetic disorders.

amniocentesis

A prenatal test that withdraws amniotic fluid for genetic analysis.

chorionic villus sampling (CVS)

A prenatal test sampling tissue from the placenta for genetic analysis.

noninvasive prenatal diagnosis (NIPD)

A prenatal test that samples maternal blood to analyze for genetic disorders.