Incomplete and co dominance
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This document discusses three genetic inheritance patterns: dominance, incomplete dominance, and co-dominance. Dominance occurs when one allele is expressed over the other. In incomplete dominance, the heterozygous phenotype is intermediate between the two homozygous phenotypes. Examples include flowers and hair color. Co-dominance occurs when both alleles are fully expressed in the heterozygote, so the phenotype shows traits of both. Examples given are coat color in horses and cattle, and chestnut and white coat colors producing a palomino horse.
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Incomplete and co dominance
- 1. INCOMPLETE DOMINANCE & CO- DOMINANCE
- 2. DOMINANCE • Dominance is a relationship between alleles of one gene, in which one allele is expressed over a second allele at the same locus. • The first allele is dominant and the second allele is recessive. • Dominance is a key concept in Mendelian inheritance.
- 3. INCOMPLETE DOMINANCE • Incomplete dominance (also called partial dominance) occurs when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes. • Examples are: - Snap Dragons or Four O’Clocks or Morning Glory or Primrose (Flowers) - A child with wavy hair as a result of one parent’s curly hair and the other’s straight hair. - Tay- Sachs disease
- 4. EXAMPLE OF INCOMPLETE DOMINANCE • A snapdragon flower that is pink flower as a result of cross- pollination between a red flower and a white flower when neither the white or the red alleles are dominant. Genotypic ratio = 1RR: 2RW : 1WW Phenotypic ratio = 1Red : 2Pink : 1White
- 5. CO-DOMINANCE When both alleles of a pair are fully expressed in a heterozygote, they are called co-dominant alleles. Such alleles exhibit a unique pattern of expression with heterozygous being phenotypically distinguishable from both of the homozygous and expressing both alleles equally. Examples are: • Roan coat color in horses and cattle • Chestnut and White color in horses are both dominant traits; the heterozygous individual is a palomino (golden).
- 6. EXAMPLE OF CODOMINANCE • C= Color gene • CR CR = Red CW CW = White CR CW = Red Roan Genotypic Ratio = All CR CW Phenotypic Ratio = All Red Roan
- 7. EXAMPLE OF CODOMINANCE Chestnut and White color in horses are both dominant traits; the heterozygous individual is a palomino (golden).
- 8. Thank You