WARM UP Quiz – No talking, do not look at another person’s paper or you will receive a ZERO!!!

Non-Mendelian Traits (Mendelian Exceptions) Incomplete Dominance & Co-Dominance

Incomplete Dominance The trait does not have a completely dominant allele, and a cross between organisms with two different phenotypes results in a third phenotype. Heterozygous offspring display a third phenotype that is a blending of the parental traits Ex: Red (RR) x White (WW) Offspring: Pink (RW)

Incomplete Dominance C. EX: If a homozygous red flowered snap dragon plant (RR) is crossed with a homozygous white flowered snap dragon plant (WW), all of the offspring will have pink flowers. RED flower x WHITE flower  PINK flower RW RW RW RW

Incomplete Dominance RR BB In another flower, if red ____ and blue ____ flowers are crossed, they produce a 3rd purple flower (RB). What would be the genotype ratio and phenotype ratio if you crossed two purple flowers? RR BB http://www.gwu.edu/~darwin/BiSc150/One/rose.GIF

Incomplete Dominance Cross of two purple flowers ____ X ____ What are gamete possibilities? genotype ratio 1RR : 2RB : 1BB phenotype ratio 1red : 2 purple : 1 blue Can you have a heterozygous red or hybrid blue flower? ___ RB RB R B RR RB R red purple http://www.gwu.edu/~darwin/BiSc150/One/rose.GIF BB RB B purple blue no

Codominance Heterozygous Offspring: RB – red and blue striped The trait does not have only one dominant allele, but has two or more dominant alleles. When both are present, the individual displays both traits at the same time. Parents: Red (RR) x Blue (BB) Heterozygous Offspring: RB – red and blue striped

Codominance EXAMPLE: If a homozygous red flowered snap dragon plant (RR) is crossed with a homozygous white flowered snap dragon plant (WW), all of the offspring will have red and white flowers. RED flower x WHITE flower  RED & WHITE flower http://www.ccs.k12.in.us/chsteachers/Amayhew/Biology%20Notes/beyond%20dominance%20notes_files/image004.jpg

Codominance Andalusian chickens also show this pattern of inheritance. If you cross a black (BB) chicken with a white (WW) chicken: You get black&white speckled (BW) chicken

Human Codominance EX: Sickle-Cell Red Blood Cells An individual who is heterozygous for sickle-cell alleles will express BOTH normal and abnormal shaped blood cells Normal RBC are disk shaped and abnormal are half moon or sickle shaped. Abnormally shaped blood cells slow blood flow, block vessels, and result in tissue damage and pain. Normal red blood cell Sickle cell

Human Codominance Blood Types Blood type is determined by multiple alleles. This means there are more than two types of alleles possible that can make up a pairing. Allele A: red blood cells produce A antigens (protein) on the outside of the cell Allele is expressed IA because it is co-dominant Allele B: red blood cells produce B antigens (protein) on the outside of the cell Allele is expressed IB because it is co-dominant Allele 0: red blood cells will NOT produce an antigen (protein) Allele is expressed i because it is recessive

Human Codominance Blood Types If given a blood transfusion of the wrong blood type, some types are incompatible and the red blood cells will clump together / clot causing death. Your immune system (antibodies) recognize the red blood cells belonging to you. If cells with a different type of antigen enter your body, your immune system will attack them.

Multiple Alleles O A B AB There are four different phenotype blood groups: A, B, O, & AB They are produced by three different alleles: A, B, and O Which ones are homozygous? Which ones are heterozygous? Phenotype All Genotypes Possible Type A (Dominant) IAIA (AA), IAi (AO) Type B (Dominant) IBIB (BB), IBi (BO) Type AB (Codominant) IAIB (AB) Type O (recessive) ii (OO) A B O AB

Multiple Alleles Sample problems of Blood type crosses