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!

+

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)

Red (RR)

White (WW)

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