Incomplete dominance and codominance Inheritance patterns that are

Incomplete dominance and codominance Inheritance patterns that are different from that seen in straight dominantrecessive traits

Incomplete Dominance F 1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. Therefore there is a third blended phenotype. Example: snapdragons (flower colour) red (RR) x white (R’R’) R R RR = red flower R’R’= white flower R’ R’

Incomplete Dominance R R R’ RR’ produces the F 1 generation R’ RR’ All RR’ = pink (heterozygous individuals display an intermediate phenotype - pink. )

Codominance Two alleles are expressed (multiple alleles) alleles in heterozygous individuals Example – petunia flowers can show codominance If a purple flowered petunia is crossed with a white flowered petunia, purple and white flowered offspring will result.

Petunia cross Purple petunia (PP) x white petunia (WW) W W P P PW PW produces the F 1 generation All PW = purple and white (heterozygous individuals display both phenotypes)

Blood type in humans is an example of a codominant trait Blood type 1. 2. 3. 4. type A B AB O = = IAIA (AA) or IAi (AO) IBIB (BB) or IBi (BO) IAIB (AB) ii (OO)

Codominance Example: homozygous male B (IBIB) x heterozygous female A (IAi) IB IB IA I AI B i I Bi 1/2 = IAIB 1/2 = IBi

Codominance Example: male O (ii) x female AB (IAIB) IA IB i I Ai I Bi 1/2 = IAi 1/2 = IBi

Codominance Question: Question If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents. boy - type O (ii) X girl - type AB (IAIB)

Codominance Answer: IA IB i i I AI B ii Parents: genotypes = IAi and IBi phenotypes = A and B

Answer Questions # 1 -6 on page 244