Types of Dominance Simple, Incomplete, & Co- dominance, Multiple Alleles, and Polygenic Traits Simple, Incomplete, & Co- dominance, Multiple Alleles, and Polygenic Traits

Simple dominance Simple dominance is when one allele is ALWAYS stronger than a second allele. Genotypes RR and Rr would BOTH show the phenotype “ round” The recessive phenotype, “wrinkled”, will only show with genotype rr. Rr r R RR Rr rr

Simple dominance o Genotypes present? _____, _____, and _____ Rr r R RR Rr rr o Phenotypes present? _______ and o ________ o Genotypic Ratio? _________________ o Phenotypic Ratio? ________________ RR Rr rr 1 RR: 2 Rr: 1 rr 3 Round : 1 Wrinkled

Simple dominance o Traits that exhibit Simple Dominance: o Widow’s Peak o Dimples or No Dimples o Curly hair or Straight hair o Yellow or Green Peas o Wrinkled or Round Peas

Incomplete Dominance A third phenotype is produced, and is a BLENDING of the two other alleles. RR W W WR WR WR WR porpax.bio.miami.edu

Incomplete Dominance o Note: The alleles are represented differently RR W W WR porpax.bio.miami.edu o Genotypic Ratio: _____________ o Phenotypic Ratio: 4 WR: 0 WW: 0 RR 4 Pink: 0 white: 0 red

Incomplete Dominance o Traits that exhibit Incomplete Dominance: o Snapdragon color (Red+White = PINK) o Sickle Cell Anemia (Sickle Cell+Normal = some Sickle & some Normal) o Fur length in Rabbits (Long+Short = Medium)

Co-Dominance Both alleles will express themselves completely, NO BLENDING. Examples: o Horse Color o Blood Types o Chicken Color

Co-dominance BB W W WB B Genotypic Ratio? 100% heterozygous Phenotypic Ratio? 100% Speckled

Multiple Alleles Traits that can have many different alleles (not just 1 dominant and 1 recessive) Hair color in Mice: 5 alleles Agouti A; black A b ; albino A a ; gray A g ; brown A br Blood Type in Humans: 3 alleles: A= Type A blood (dominant) A= Type A blood (dominant) B= Type B blood (dominant) B= Type B blood (dominant) O= Type O blood (recessive) O= Type O blood (recessive)

GenotypesPhenotypes AA or AOType A BB or BOType B ABType AB OOType O Check out possible genotypes and phenotypes of blood:

If you have AB as your genotype, you have both Type A and Type B blood, also known as Type AB If you have AB as your genotype, you have both Type A and Type B blood, also known as Type AB If you have AO, O is recessive to A, so you have type A blood If you have AO, O is recessive to A, so you have type A blood Q. When would you have Type O blood? Q. When would you have Type O blood? A. When you have OO as your genotype. A. When you have OO as your genotype. Blood exhibits both Multiple Alleles and Co-Domiance

Multiple Alleles: Blood Type AA B B AB porpax.bio.miami.edu OA B O OO BO AO AB  MANY DIFFERENT GENOTYPES AND PHENOTYPES !

Polygenic Traits Traits that are affected by more than one GENE Examples: Skin Color (2 genes) Key # Genotype Phenotype 1 M1M1M2M2 Black Skin 2 M1M1M2m2 Dark Brown Skin 3 M1M1m2m2 Brown Skin 4 M1m1m2m2 Light Brown Skin 5 m1m1m2m2 White Skin

Polygenic Traits – traits controlled by 2 or more genes that interact, forming the trait  Usually show a wide range of phenotypes  Ex: Skin color, eye color, foot size, height  Wide range of skin colors because there are more than 4 genes that control this trait.

Nature vs. Nurture Traits may be influenced by the environment, for example height. If not given the proper nutrition as a child, they might not be as tall as their genes dictate.