Genetics explores how biological information is stored, inherited, changed, and expressed in living things.
Genetics is a branch of biology that studies heredity and variation. It helps explain why children resemble their parents, why siblings can still be different from one another, how cells carry instructions, and how changes in DNA can influence traits. Modern genetics connects ideas from cell biology, evolution, medicine, agriculture, and biotechnology.
DNA is the molecule that stores most hereditary information in living organisms.
Learn MoreGenes are stretches of DNA that contribute to making functional products and influencing traits.
Learn MoreChromosomes organize long DNA molecules so genetic information can be copied and passed on.
Learn MoreParents pass genetic information to offspring through reproductive cells.
Learn MoreGenetic differences help create the diversity seen within populations and species.
Learn MoreMutations are changes in DNA that can be harmless, harmful, beneficial, or have no noticeable effect.
Learn MoreDNA, short for deoxyribonucleic acid, carries biological information in a chemical code. Its famous double-helix structure is built from two strands made of repeating units called nucleotides. Each nucleotide contains one of four bases: adenine, thymine, cytosine, or guanine. The order of these bases forms information that cells can copy and use. Before many cells divide, their DNA is replicated so each new cell receives a set of genetic instructions.
A gene is a region of DNA associated with a functional product, often a protein or a functional RNA molecule. Proteins perform countless jobs, including building cell structures, speeding up chemical reactions, and sending signals. A single visible trait is not always controlled by one gene; many traits result from interactions among numerous genes and environmental influences. This is why simple inheritance patterns are useful for learning basic genetics but do not explain every characteristic in a living organism.
DNA molecules can be extremely long, so cells package them with proteins into structures called chromosomes. In humans, most body cells normally contain 23 pairs of chromosomes, for a total of 46, although reproductive cells normally contain one chromosome from each pair. Chromosomes help organize genetic material during cell division. Different species have different chromosome numbers, and having more chromosomes does not mean an organism is more complex.
Inheritance describes how genetic information moves from parents to offspring. During sexual reproduction, offspring receive genetic material from two parents, creating new combinations of genetic variants. Gregor Mendel's experiments with pea plants helped reveal basic patterns of inheritance, including dominant and recessive relationships for some traits. Modern genetics has shown that inheritance can also involve more complex patterns such as incomplete dominance, codominance, multiple genes, sex-linked inheritance, and interactions with the environment.
Individuals of the same species are not genetically identical. Variation can arise when genetic material is shuffled during reproduction, when populations contain different versions of genes called alleles, and when mutations introduce new DNA changes. Environmental factors can also influence how traits develop, so genetic differences are only part of the story. Variation is important in evolution because natural selection acts on differences that affect survival and reproduction in particular environments.
A mutation is a change in a DNA sequence. Mutations can happen because of copying errors or exposure to certain environmental factors, and cells have repair systems that correct many DNA mistakes. Some mutations have no noticeable effect, some alter how a gene works, and a small number may contribute to disease or provide an advantage in a particular environment. When mutations occur in cells that produce eggs or sperm, they can sometimes be inherited by future generations.