Genotype cross trees and square, illustration

Genotype cross trees and square, illustration. The effects of mixing (crossing) genetic traits is shown here for flower colour (top) and cat shape and colour (bottom). An organism inherits two gene variants (alleles), one from each parent. At upper left, the flower colours red (R) and white (W) are expressed as allele pairs (RR and WW). Neither colour allele is dominant (known as co-dominance), and the crossing to produce the next generation produces four possible results, all of which are pink flower hybrids. Crossing of two pink flowers may restore the white and red flowers, as shown at upper right. For the cats, the dominant/recessive allele pairs are for shape and colour, which are independent and produce dihybrid crosses. Slender (S) is dominant over stocky (s) and black (B) is dominant over white (b). An example of a cross is at lower left (slender white crossed with stocky black), with the full Punnett square at lower right (a quarter white cats, a quarter stocky cats, and one-sixteenth stocky white cats).