COMPLEX PATTERNS OF HEREDITY Polygenic Traits traits influenced

o Incomplete Dominance – a trait that is intermediate between the two parents ex:

Incomplete Dominance: Suppose a red flower is crossed with a pink flower. What are

Codominance – two dominant traits are expressed at the same time ex: a horse

Codominance: Suppose a horse with a black coat is crossed with a horse with

o Multiple Alleles – genes with 3 or more alleles ex: 3 alleles –

Blood type inheritance is somewhat complicated, with three forms of the gene (A, B,

Blood Types: Suppose a woman with blood type AB marries a man who is

Traits Influenced by the Environment: o o hydrangea plants: acidic soil – blue flowers

o o Siamese cats: fur color is influenced by body temperature cold – dark

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COMPLEX PATTERNS OF HEREDITY Polygenic Traits: traits influenced by several genes ex: human eye color, height, weight, hair color

o Incomplete Dominance – a trait that is intermediate between the two parents ex: snapdragons - red flower is crossed with a white flower and pink flowers are produced RR – red Rr – pink rr – white ex: in humans straight hair crossed with curly hair may produce wavy hair SS – straight Ss – wavy ss – curly

Incomplete Dominance: Suppose a red flower is crossed with a pink flower. What are the chances the offspring will have red flowers? Pink flowers? White flowers? 50% 0% 50% R RR RR r Rr Rr

Codominance – two dominant traits are expressed at the same time ex: a horse with a black coat is crossed with a horse that has a white coat producing a horse that has both a black and white coat BB – black BW – black & white WW - white o

Codominance: Suppose a horse with a black coat is crossed with a horse with a white coat. What are the chances the offspring will have a black coat? White coat? Black 0% 0% and white coat? B 100% B W BW BW

o Multiple Alleles – genes with 3 or more alleles ex: 3 alleles – A, B, O 4 blood types – A, B, AB, O *Even for traits controlled by genes with multiple alleles, an individual can have only 2 of the possible alleles.

Blood type inheritance is somewhat complicated, with three forms of the gene (A, B, O), 6 possible genotypes, and 4 possible phenotypes. (A, B, AB, O) o o o AB AA - Homozygous A AO - Heterozygous A BB - Homozygous B BO - Heterozygous B OO

Blood Types: Suppose a woman with blood type AB marries a man who is heterozygous B. What are the chances that their children will have blood type A? 25% blood type B? 50% A B blood type AB? 25% B AB BB O AO BO

Traits Influenced by the Environment: o o hydrangea plants: acidic soil – blue flowers basic soil – pink flowers arctic fox: summer – produces enzymes that make pigments therefore it has a reddish brown coat winter – pigment producing genes do not function therefore the coat of the fox is white

o o Siamese cats: fur color is influenced by body temperature cold – dark coat warm – light coat humans: height - influenced by nutrition skin – exposure to the sun