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Incomplete dominance and co-dominance

Incomplete dominance and co-dominance. Inheritance patterns that are different from that seen in straight dominant-recessive traits. Incomplete Dominance.

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Incomplete dominance and co-dominance

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  1. Incomplete dominance and co-dominance Inheritance patterns that are different from that seen in straight dominant-recessive traits

  2. Incomplete Dominance F1hybrids 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’) RR = red flower R’R’= white flower R R R’ R’

  3. Incomplete Dominance R R produces the F1 generation RR’ RR’ R’ R’ RR’ RR’ All RR’ = pink (heterozygous individuals display an intermediate phenotype - pink.)

  4. Codominance Two alleles are expressed (multiple 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.

  5. produces the F1 generation All PW = purple and white (heterozygous individuals display both phenotypes) Petunia cross Purple petunia (PP) x white petunia (WW) P P W W PW PW PW PW

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

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

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

  9. Codominance 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)

  10. Codominance Answer: IA i IAIB IB i ii Parents: genotypes = IAi and IBi phenotypes = A and B

  11. Answer Questions # 1-6 on page 244

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