INCOMPLETE AND CO-DOMINANCE.pptx
- 1. GENETICS LAB
- 2. Codominance: in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic Epistasis: an interaction between genes such that one gene masks or interferes with the expression of another Hemizygous: the presence of only one allele for a characteristic, as in X- linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant Incomplete Dominance: in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype Linkage: a phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together Recombination: the process during meiosis in which homologous chromosomes exchange linear segments of genetic material, thereby dramatically increasing genetic variation in the offspring and separating linked genes Wild Type: the most commonly occurring genotype or phenotype for a given characteristic found in a population GLOSSARY
- 3. INCOMPLETE DOMINANCE (LAB) INCOMPLETE DOMINANCE Incomplete dominance (Partial Dominance) occurs when phenotype of heterozygous genotype is distinct from & often intermediate to the phenotypes of homozygous genotypes (Parents). OCCURANCE : - Snap Dragons/ 4O’Clocks/ Morning Glory/ Primrose (Flowers) - A child with wavy hair as a result of one parent’s curly hair & other’s straight hair. -Tay- Sachs disease
- 4. Snapdragons can be Red, White, or Pink (heterozygous) In Incomplete dominance - Neither allele is Dominant or Recessive, the heterozygous condition results in a "blending" of the two traits. Red X White = Pink In this graphic, just the letter R is used, Heterozygous Rr represents intermediate trait (pink) It really doesn't matter what letters you choose, as long as the intermediate trait is always the heterozygote. EXAMPLE OF INCOMPLETE DOMINANCE: A Pink snapdragon flower is a result of cross-pollination between Red Flower & White Flower, when neither white or red alleles are dominant. Phenotypic ratio=1Red:2Pink:1White Genotypic ratio= 1RR:2RW:1WW
- 5. CROSS PRACTICE: RED X WHITE = F1 & F2 ? PR & GR ? PINK X PINK = F1 & F2 ? PR & GR ? PINK X WHITE = F1 & F2 ? PR & GR ? PINK X RED = F1 & F2 ? PR & GR ?
- 6. EXAMPLE OF INCOMPLETE DOMINANCE:
- 7. CO-DOMINANCE When both alleles of a pair are fully expressed in a heterozygote, they 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. OCCURANCE : • Roan coat color in horses and cattle • Chestnut & White color in horses are both dominant traits; the heterozygous individual is a palomino (golden). Example Of Co- dominance {Suppose C=Coat Color gene} CR CR = Red Bull CW CW = White Cow CR CW = Roan Cattle P1 CRCR X CWCW G CR CW F1 CRCW Genotypic Ratio = All CR CW Phenotypic Ratio = All Roan
- 8. CROSS PRACTICE: RED X WHITE = F1 & F2 ? PR & GR ? ROAN X ROAN = F1 & F2 ? PR & GR ? ROAN X WHITE = F1 & F2 ? PR & GR ? ROAN X RED = F1 & F2 ? PR & GR ? EXAMPLE OF CO-DOMINANCE:
- 10. • Chestnut & White color in horses are both dominant traits; the heterozygous individual is a palomino (golden). EXAMPLE OF CO-DOMINANCE: