Looking at incomplete and codominance Monohybrid Crosses Looking at incomplete and codominance

Incomplete Dominance The dominant allele can’t completely hide the recessive allele, so a heterozygous genotype results in a phenotype that is a mix of the other 2 phenotypes

Example 1 In some plants, red (R) flower color is incompletely dominant over white (r) color. Show the cross between two plants heterozygous for flower color. R r R r G = RR, Rr, rr GR = 1:2:1 P = red, pink, white PR = 1:2:1 RR Rr rr

Example 2 Show the cross between a homozygous dominant and a heterozygous plant. R R R r G = RR, Rr GR = 2:2:0 P = red, pink PR = 2:2:0 RR Rr

Codominance Occurs when both alleles for a gene are expressed in a heterozygous offspring No allele is dominant or recessive

Example 1 In horses, red coat is codominant with white coat. Show the cross between a red (R) horse and a white horse (R’). R R R’ G = RR’ P = Roan GR = 0 (RR): 4 (RR’): 0 (R’R’) PR = 0:4:0 RR’

Example 2 Show the cross between a white horse and a roan horse. R’ R’ G = RR’, R’R’ P = roan, white GR = 0:2:2 PR = 0:2:2 RR’ R’R’