Incomplete Dominance Codominance and Multiple Alleles INCOMPLETE DOMINANCE

Incomplete Dominance, Codominance and Multiple Alleles

INCOMPLETE DOMINANCE Incomplete Dominance- Pattern of gene expression in which the phenotype of a heterozygous individual is intermediate between those of the parents. • Cases in which one allele is not completely dominant over another. Example: Snapdragons and Carnations

Incomplete Dominance- F 1 generation

Incomplete Dominance- F 2 generation

CODOMINANCE Codominance- The condition in which both alleles in a heterozygous organism are expressed. • BOTH alleles contribute to the phenotype. • The two alleles don’t blend, but are rather both present in the offspring. Examples- Checkered Chickens, Roan Horses, Roan Cows, Variegated Clover.

Codominance Checkered White chicken Black B W W Black chicken BW Checkered B BW Checkered

Roan Horse http: //search. vadlo. com/b/q? rel=2&keys=Dominance+Incomplete+Dominance+Codominance+PPT

Roan Cattle http: //www. ccs. k 12. in. us/chsteachers/BYost/Biology%20 Notes/CH 11 notescoincompletedom_files/image 004. jpg Variegated Clover http: //3. bp. blogspot. com/_z. UPrg. MM 5 t. Ug/SSVdrs 59_u. I/AAAAA 8/q. JGj. G 2 n. ZPhk/s 200/codominance. GIF

Multiple Alleles- Genes which have more than two alleles. It is common for more than 2 alleles to control a trait in a population Multiple alleles can only be studied in populations since each individual only has 2 alleles for a trait. Examples: human blood types, fruit fly eye color, coat color in rabbits: C, cch, and c.

Chapter 11 Complex Inheritance and Human Heredity 11. 2 Complex Patterns of Inheritance Coat Color of Rabbits Chinchilla Albino Light gray Dark gray Himalayan

ABO Blood Type • ABO blood type in humans is determined by three alleles: IA I B i • IA and IB are codominant alleles. • Both IA and IB are dominant to the allele i. Blood Genotype Type IA IA i A IB IB i B IA IB AB ii O

Chapter 11 Complex Inheritance and Human Heredity 11. 2 Complex Patterns of Inheritance Multiple Alleles Blood groups in humans ABO blood groups have three forms of alleles.

Donor-recipient compatibility Recipient Type A B AB O A Donor B AB O Note: = Unsafe • Type O blood may be transfused into all the transfusion other types = the universal donor. = Safe transfusion • Type AB blood can receive blood from all the other blood types = the universal recipient. © 2007 Paul Billiet ODWS