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Published byLiana Hermanto Modified over 6 years ago
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Beyond Mendelian Genetics: Incomplete Dominance
Mendel was lucky! Traits he chose in the pea plant showed up very clearly… One allele was dominant over another, so phenotypes were easy to recognize. But sometimes phenotypes are not very obvious…
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Incomplete Dominance Snapdragon flowers come in many colors.
If you cross a red snapdragon (RR) with a white snapdragon (rr) You get PINK flowers (Rr)! R R r r Genes show incomplete dominance when the heterozygous phenotype is intermediate (a blend of the two alleles). R r
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Incomplete dominance R r R r
When F1 generation (all pink flowers) is self pollinated, the F2 generation is 1:2:1 red, pink, white Incomplete Dominance R r R R R r r r R r
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Incomplete dominance What happens if you cross a pink with a white?
A pink with a red?
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Mendelian Genetics 2/23/2019 Codominance Two alleles are expressed (multiple alleles) in heterozygous individuals. Example: blood type Phenotye Genotype(s) 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii copyright cmassengale
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Mendelian Genetics 2/23/2019 Codominance Problem Example: homozygous male Type B (IBIB) x heterozygous female Type A (IAi) IB IA i IAIB IBi 1/2 = IAIB 1/2 = IBi copyright cmassengale
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Another Codominance Problem
Mendelian Genetics 2/23/2019 Another Codominance Problem Example: male Type O (ii) x female type AB (IAIB) i IA IB IAi IBi 1/2 = IAi 1/2 = IBi copyright cmassengale
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Mendelian Genetics 2/23/2019 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) girl - type AB (IAIB) copyright cmassengale
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Mendelian Genetics 2/23/2019 Codominance Answer: IB IA i IAIB ii IAi Parents: genotypes = IAi and IBi phenotypes = A and B IAi copyright cmassengale
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