UNIT 4: Genetics What are the different patterns of heredity: Incomplete Dominance, Codominance, and Multiple Alleles?   **Not all traits are represented by alleles, in which one allele is completely dominant over the other like in COMPLETE DOMINANCE - In INCOMPLETE DOMINANCE, an individual shows an intermediate phenotype that is a ‘blending’ of the two parents.

Incomplete dominance Examples Straight hair x Curly hair = Wavy hair Round shape x Long shape = Oval shape Small nose x Large nose = Medium nose

Incomplete Dominance Snapdragon example: Plants with red flowers are homozygous for red color ( RR) Plants with white flowers are homozygous for white color ( rr) A heterozygous flower will be a pink color ( Rr) * Notice that none of the alleles are recessive but none of them are completely dominant either (hence the name incomplete dominance)

Incomplete Dominance Complete the punnett square below to show the results of crossing a red snapdragon with a white snapdragon. Key: RR=red RR x rr Rr=pink R R rr=white r What is the phenotype of the F1 offspring? 100% Pink   Rr

Incomplete Dominance Now, cross two of the F1 generation offspring to determine the F2 generation. Key: RR=red Rr=pink R r rr=white R r What is the phenotypic ratio & percentage of the offspring? 25%Red: 50%Pink: 25%white RR  Rr rr

Codominance In CODOMINANCE, an individual expresses BOTH forms of trait, and NOT in a blended form (like in incomplete dominance). Instead, both alleles are expressed equally Example Chickens with black feathers are homozygous for black color ( BB) Chickens with white feathers are homozygous for white color ( bb) A heterozygous chicken will be a checkeredcolor ( Bb) (black and white)

Codominance Complete the punnett square below to show the results of crossing a checkered rooster with a white hen. Key: BB=black B b Bb=checkered bb=white b b What is the phenotypic ratio & percentage of the offspring? 50% checkered: 50%white Bb  bb Bb

Multiple Alleles Some traits are controlled by genes with 2 or more alleles. These genes are said to have multiple alleles. ** Remember: For each trait, an individual inherits 2 alleles for a trait. Example of a trait controlled by genes with multiple alleles: BLOOD TYPE ** There are 3 alleles that determine human blood type: A, B, and O Different combination of these 3 alleles can produce four different blood types: A B _ __AB___ ___O___

Multiple Alleles ** Remember: Even for traits controlled by genes with multiple alleles, an individual can have only 2 of the possible alleles for that gene. Blood Type Possible Genotypes  A IAIA, IAi B IBIB, IBi AB IAIB O ii

Multiple Alleles Practice Problems A woman with blood type A has a child with blood type AB. She says a man with blood type B is the father. Could he be the father? Yes If so, what is the probability that the man is the father? IAi x IBi=25%AB; IAIA x IBIB=100%AB P1 = IAi x IBi

Multiple Alleles Use the information to answer the following questions. Do punnett squares below to prove your answers! Be sure to number your punnett squares according to the # of the question. PARENTS CHILDREN The John’s= type O & type AB Baby 1 is type AB The Klumpp’s = type A & type B Baby 2 is type O The Templet’s= type A & type O Baby 3 is type B

Multiple Alleles 1. Who are the parents of baby 1? The Klumpp’s PARENTS CHILDREN The John’s= type O & type AB Baby 1 is type AB The Klumpp’s = type A & type B Baby 2 is type O The Templet’s = type A & type O Baby 3 is type B 1. Who are the parents of baby 1? The Klumpp’s 2. Who are the parents of baby 2? The Templet’s 3. Who are the parents of baby 3? The John’s