As early plant breeders changed the carrot's color, they changed its genes. Orange color in the carrot root is best explained with a two gene model.The first gene, called Y, is a dominant gene that blocks production of yellow and orange pigments. In other words, a non-pigmented, white carrot is the dominant trait. An orange carrot requires two recessive copies of the Y gene. A second gene, called Y2, determines whether orange pigments accumulate in the root. An orange carrot has two recessive copies at two genes: yy and y2y2. Recent
sequencing of the carrot genome identified a likely candidate for the Y gene—linking the genetic model to the carrot genome.
Modern plant breeders continue to improve orange color, or more specifically the beta-carotene levels in carrot roots. Increasing the amount of beta-carotene in carrot increases its nutritional content. Since the 1970s, plant breeders have increased beta-carotene levels by 40%, simply by selecting for deeper, stronger orange color. Beta-carotene is especially important to humans because the human body converts it into retinal and then into Vitamin A or retinol. Vitamin A plays important roles in vision, the immune system, skin health and bone growth.