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

 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? R R R Rr RR r

 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

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 and white coat? W B B BW W

 Multiple Alleles – genes with 3 or more alleles ex: blood type – A, B, AB, O 3 alleles – A, B, 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 and 4 possible phenotypes. (A, B, AB, O)  AB – Blood Type AB  AA – Blood Type A  AO – Blood Type A  BB – Blood Type B  BO – Blood Type B  OO – Blood Type O

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

Traits Influenced by the Environment:  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

 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

Genetic Disorders: The harmful effects produced by inherited mutations. Mutations:  *changes in genetic material  *occurs when a gene is damaged, copied incorrectly, or a faulty protein was made

Examples of Genetic Disorders  Sickle Cell Anemia – autosomal recessive (red blood cells are sickle-shaped)  Cystic Fibrosis – autosomal recessive (production of thick sticky mucus – affects lung)  Huntington’s Disease – autosomal dominant (neurodegenerative disorder)  Hemophilia – sex linked recessive (rare bleeding disorder)

Sickle Cell Anemia  Sickle cell anemia is an autosomal recessive disorder. Jane is normal and does not carry the gene whereas here husband does have the disease. What percentage of their children will have sickle cell anemia? S ssss Ss 0%

Huntington’s Disease  Huntington’s is an autosomal dominant disorder. Karen is heterozygous for the disorder and she marries a man who does not have the disorder. What percentage of their children will have Huntington’s? H h hhhh hh 50% When a disorder is autosomal dominant, can there be any carriers? No !!

 Genetic Counseling – a form of medical guidance that informs people about genetic problems that could affect them or their offspring  Genetic Therapy – allows scientists to correct certain recessive genetic disorders by replacing defective genes with copies of healthy ones