1	Incomplete Dominance, Codominance, and ABO Blood Types
2	Review of Simple Mendelian Genetics Law of Segregation: each gene has two different alleles that are separated when gametes form One allele goes to one gamete and the other allele to a different gamete Law of Independent Assortment: genes for different traits are inherited independently from each other
3	Review of Simple Mendelian Genetics Dominant vs. Recessive alleles for a gene The dominant allele masks the recessive one, so you see the dominant trait (for RR or Rr) The only way to see a recessive trait is to have two recessive alleles (rr) Dominant allele is represented as a capital letter (R) Recessive allele is represented as a lowercase letter (r)
4	Unfortunately, it’s not all that easy…
5	Incomplete Dominance Sometimes neither allele is fully dominant over the other Incomplete Dominance: neither allele is dominant but combine and display a new trait that is a mixing of the two alleles
6	Incomplete Dominance
7	Incomplete Dominance In incomplete dominance, the two alleles are represented as Two capital letters, one with an apostrophe to indicate the different allele that is involved Ex. R (for the red allele) and R’ (for the white allele) When these two alleles come together, they portray a mixing of the two phenotypes!
8	Codominance Other times both alleles are fully dominant Codominance: both alleles of a gene are dominant and the heterozygous phenotype has both traits equally expressed
9	Codominance
10	Codominance In codominance the two alleles are represented as Two capital letters: Use the first letter of one trait (B for Brown) and the first letter of the other trait (W for White) When they come together as a heterozygote, both traits show as the phenotype
11	Let’s Stop and Think… Let’s say there are two alleles for the hair color trait- red and blue What would be the resulting phenotype of a heterozygous pair if the alleles showed incomplete dominance? A. Red B. Blue C. Purple D. Red and Blue patches
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13	Multiple Alleles Sometimes there are more than two alleles that govern the phenotype of a trait Multiple Alleles: the presence of more than two alleles for a genetic trait
14	Multiple Alleles Blood Type Human blood type is governed by the presence of 3 different alleles: A B O However, each person only has 2 of these 3 alleles in their DNA
15	ABO Blood Type Blood types follow both Codominant and simple Dominant inheritance The A allele and B allele are codominant with each other The A allele and B allele are both purely dominant over the O allele The O allele is recessive
16	Which blood type are you if you have… AA Type A blood BB Type B blood AB Type AB blood AO Type A blood BO Type B blood OO Type O blood
17	ABO Blood Types The blood type gene and alleles are represented differently than you have seen before The blood type gene is I For this I gene you can have the following alleles: For A: I^A For B: I^B For O: i
18	Let’s stop and think… What are the two allele combinations you can have for type A blood? I^AI^A and I^ai What are the two allele combinations you can have for type B blood? I^BI^B and I^Bi
19	Let’s Stop and Think… What is the only allele combination you can have for type AB blood? I^AI^B What is the only allele combination you can have for type O blood? ii