Genetic Modification

Genetic Manipulation (selection)

Genetic modification of organisms has been occurring through human manipulation since the beginning of agriculture. Humans selectively bred crops and livestock to propagate desirable traits in a process termed artificial selection. The original grass that gave rise to domesticated corn called teosinte hardly resembles what we think of when imagining modern maize.


Teosinte, the progenitor of maize. Corn came about due to selective breeding. Credit: John Doebley (CC-BY)

Variation: Crop domestication

Selective breeding can yield a variety of features even within the same species. Below is selection of vegetables of the species Brassica oleracea that have been developed into different varieties over the course of agricultural history.

Starr 070730-7852 Brassica oleracea var. capitata

Cabbage: Brassica oleracea var. capitata Credit: Forest & Kim Starr (CC-BY 3.0)

Brocoli 02

Broccoli: Brassica oleracea var. italica Credit: Coyau (CC-BY-SA 3.0)

Chou-rave 01

Kohlrabi: Brassica oleracea var. gongylodes Coyau (CC-BY-SA 3.0)

Romanesco Brassica oleracea Richard Bartz

Romanesco: Brassica oleracea var. botrytis Credit: Richard Bartz (CC-BY-SA 2.5)

Variation: Animal domestication

Dog morphological variation

Credit: Mary Bloom, American Kennel Club (CC-BY-SA 4.0)

Collage of Nine Dogs
Companion animals like dogs underwent thousands of years of domestication and selection for traits that were desirable for different circumstances. A high degree of morphological diversity exists between dog breeds and their ancestral grey wolf progenitor.

Genetic Manipulation (engineered)

Artificial selection takes multiple generations over a long period of time. With the advent of recombinant DNA and biotechnology, scientists can now genetically modify organisms through introduction of foreign genes to provide desirable characteristics within one generation. This process does not require traits to naturally arise in a species.



GloFish are transgenic zebra fish (Danio rerio) expressing variants of GFP. Bottom features a wild-type fish. Credit: Azul (CC-BY)

GloFish® are novelty pets that have the insertion of various cnidarian fluorescent protein genes into the genome. These fish were released in the United States in 2003 and have subsequently been developed in red, orange, and blue varieties. Black tetras and tiger barbs are also now available.

The perks of working for a pet company... I brought home a GloFish tank and a bunch of fish! Yes these fish actually glow under black light. #GloFish #Tetra #Fish #Aquarium

Black tetra (Gymnocorymbus ternetzi) GloFish Credit: (CC-BY 2.0)


Wild-type Black Tetra Credit: Fernandograu (CC-BY-SA 3.0)