Inheritance Patterns

Incomplete Dominance The heterozygous (hybrid) phenotype is somewhere in-between the homozygous phenotypes If R = red and r = white Rr = pink

We still use capital (dominant) and lowercase (recessive) letters And the same letter!

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Co-Dominance Both alleles of a gene are expressed – Equal dominance (like co-workers) We write alleles as 2 different capital letters BB = Black feathers WW = White feathers BW = Speckled black and white feathers

Black (BB) White (WW) Black & White (BW)

White (WW) Red (RR) Roan (RW)

Multiple Alleles A gene that is controlled by 3 or more alleles Blood Groups – ABO IA :has only antigen A IB : has antigen B i: has neither antigens = Type O IAIB : has both A and B antigens

Blood Transfusions Recipient – receives blood Donor – donates blood You can only receive blood that has the same antigens on its cells

Rh Antigen Rh antigen is also found on red blood cells Do not have antigen = Rh negative Have antigen = Rh positive

Sex-Linked Females = XX Males = XY If a trait is carried on the X chromosome, a male has only 1 copy It is more likely that a recessive trait will show up on a male than a female. Why?

Polygenic Traits Many genes are involved in controlling the phenotype