DNA (Deoxyribonucleic Acid): The molecule that carries genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms.

Gene: A segment of DNA that contains coding information for the synthesis of proteins, which determine traits in an organism.

Chromosome: A thread-like structure composed of DNA and protein that contains genes; humans have 23 pairs of chromosomes.

Genome: The complete set of genes or genetic material present in a cell or organism.

Mutation: A change in the DNA sequence that can lead to variations in traits or cause genetic disorders.

Genotype: The genetic constitution of an individual organism, often contrasted with phenotype.

Phenotype: The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.

Allele: One of two or more versions of a gene that are found at the same place on a chromosome.

Dominant Trait: A genetic trait that is expressed in the phenotype even when only one copy of the gene is present.

Recessive Trait: A genetic trait that is expressed only when two copies of the gene are present.

Genetic Variation: Differences in DNA sequences among individuals within a population, leading to diversity in traits.

Mendelian Inheritance: The pattern of inheritance that follows the laws formulated by Gregor Mendel, based on the segregation and independent assortment of genes.

Genetic Engineering: The deliberate modification of the characteristics of an organism by manipulating its genetic material.

CRISPR-Cas9: A powerful tool for editing genomes, allowing researchers to alter DNA sequences and modify gene function.

Epigenetics: The study of changes in gene expression that do not involve alterations to the underlying DNA sequence.

Genetic Disorder: A disease or condition caused by an abnormality in an individual's DNA.

Heritability: The proportion of observed variation in a particular trait among individuals in a population that is due to genetic differences.

Genetic Linkage: The tendency of genes located close together on a chromosome to be inherited together.

Polygenic Traits: Traits that are controlled by multiple genes, often contributing to complex traits like height and skin color.

Genome Sequencing: The process of determining the complete DNA sequence of an organism's genome at a single time.