Incomplete Dominance One allele cannot completely dominate the other A new trait is produced Incomplete Dominance Incomplete Dominance Example snapdragons flower red R ID: 1048695
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1. Genetics : Special Cases
2. Incomplete DominanceOne allele cannot completely dominate the other.A new trait is produced
3. Incomplete Dominance
4. Incomplete DominanceExample: snapdragons (flower) red (R) x white flower (r) RR = red flower rr = white flower Rr = pink flowerrrRR
5. RrRrRrRrrrRRIncomplete DominanceGenotypes: RrGenotypic Ratio: all alikePhenotypes: PinkPhenotypic Ratio: all alike
6. Incomplete DominanceExample: snapdragons (flower) red (R) x white flower (r) RR = red flower rr = white flower Rr = pink flowerRrRr
7. RrRrIncomplete DominanceGenotypes: RR,Rr,rrGenotypic Ratio:1 : 2 : 1Phenotypes:Red : Pink : WhitePhenotypic Ratio:1 : 2 : 1RRRrRrrr
8. Incomplete DominanceIn snapdragons, red (RR) flowers and white flowers (WW) are incompletely dominant and when crossed produce a new phenotype: pink flowers (RW). Cross a red (RR) flower with a pink flower (RW)What is the probability of having white offspring?What is the probability of having Pink offspring?What is the probability of having Red offspring?What is the probability of having Heterozygous offspring?What is the probability of having Homozygous offspring?
9. CodominanceWhen both dominant alleles show in the offspring
10. Sex – Linked TraitsTraits (genes) located on the sex chromosomesXX genotype for femalesXY genotype for malesSex – linked traits are usually carried on the X chromosome
11. Sex ChromosomesXX chromosome - femaleXy chromosome - malefruit flyeye colorExample: Eye color in fruit fliesSex – Linked Traits
12. Example: Eye color in fruit flies (red-eyed male) x (white-eyed female) XRY x XrXrRemember: the Y chromosome in males does not carry this trait.RR = red eyedRr = red eyedrr = white eyedXy = maleXX = femaleXrXR yXrSex – Linked Trait Problem
13. XR XrXR XrXr yXr y50% red eyed female50% white eyed maleXrXR yXrSex – Linked Trait
14. Multiple Allele TraitsTraits having more than one allele that can be found in a populationExample: Human Blood Types has 3 alleles rather than 2There are fourdistinctly differentBlood types
15. Example: homozygous female Type B (IBIB) x heterozygous male Type A (IAi)IAIBIAIBIBiIBiGenotypes= IAIB, IBiGenotypic Ratio=2:2Phenotypes=AB,BPhenotypic Ratio=2:2IAIBIBiMultiple Allele Problem
16. Example: male Type O (ii) x female type AB (IAIB)IAiIBiIAiIBi1/2 = IAi1/2 = IBi iIAIBiMultiple Allele Problem
17. 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)Multiple Allele
18. Answer:IAIBiiParents:genotypes = IAi and IBiphenotypes = A and BIBIAiiMultiple Allelle
19. Female Carriers
20. Polygenic TraitsTraits that are controlled by several genes at the same timeExample: Human Eye ColorAlleles : A, a, B, b, C, c Dark Brown = AABBCC Green = AaBbCc Light Blue = aabbcc