Multiple Alleles Eye color in Drosophila (fruit flies) For each trait observed by Mendel…. Only 2 alleles existed (T & t, for example) Many traits are controlled by multiple alleles 2 examples include Eye color in Drosophila (fruit flies) Blood types in humans

Eye Color in Drosophila 4 alleles control eye color E1 = Wild E2 = Apricot E3 = Honey E4 = White E1 > E2 > E3 > E4

Normal Fruit Fly

Mutant Fruit Flies                                              Short winged fly Normal fruit fly Curly winged fly

Eye Color in Drosophila Phenotypes Genotypes Wild Type E1E1, E1E2, E1E3, E1E4 Apricot E2E2, E2E3, E2E4 Honey E3E3, E3E4 White E4E4

E3 E4 E4 E4 E3E4 E4E4 E3E4 E4E4 Phenotypes Genotypes 2 E3E4 : 2 E4E4 Predict the phenotypic outcome if a honey colored heterozygous fly is crossed with a white fly! E3 E4 E4 E3E4 E4E4 E4 E3E4 E4E4 Phenotypes 2 Honey : 2 White Genotypes 2 E3E4 : 2 E4E4

? ? ? ? E1E2 E1E3 E2E3 E3E3 Genotpes E1E3 : E2E3 Phenotypes What are the possible phenotypes of the parents in a cross which produces the following offspring? ? ? ? E1E2 E1E3 ? E2E3 E3E3 Genotpes E1E3 : E2E3 Phenotypes Wild & Apricot

Another Example of Multiple Alleles Possible alleles C cch ch c

Antigen type Determines Blood type Blood Types

Person with blood type A Has antigen A on RBC’s & Antibody B (floating in plasma) A A A A A A A A A A

i is recessive to IA and IB Blood Typing in Humans Another example of multiple alleles Controlled by 3 alleles IA, IB and i IA and IB are said to be codominant If a person inherits both of them, then antigen A and antigen B are on the RBC’s i is recessive to IA and IB

Blood Components Antigens A, B or Rh may be present on RBC surface

Genotypes and Phenotypes for ABO Blood Types Genotype Phenotype Blood Type IAIA, IAi A antigen A IBIB, IBi B antigen B IAIB A & B antigen AB ii neither antigen 0

IA IB i i IAi IBi IAi IBi Phenotypes Genotypes 2 IAi : 2 IBi Predict the phenotypic outcome if a person with blood type AB mates with a person with type O! IA IB i IAi IBi i IAi IBi Phenotypes 1 Type A : 1 Type B Genotypes 2 IAi : 2 IBi

Blood Typing Problem 1 IB__ IBIB or IBi Dad Mom Unknown Blood Type A Must carry IB__ IBIB IBi IAIB IAIA or IA i Baby Blood Type B IBIB or IBi

Blood Typing Problem 1 i__ ii Dad Mom Unknown Blood Type B Blood Type Must carry i__ IBi IAi ii IBIB or IB i Baby Blood Type O ii

Punnet Squares for Codominance

IA IB i i Must Use Product Rule IAi IBi IAi IBi Probability of Calculate the probability of producing a son who is blood type A from the following cross! IA IB Must Use Product Rule Answer 0.5 X 0.5 = 0.25 or 25% i IAi IBi i IAi IBi Probability of producing a son = 0.5 Prob. Of producing Type A = 0.5

Blood Typing and Gender Calculate the probability of producing a daughter who is blood type A from a cross between a Type B mother and a Type A father, given that each of these individuals have a parent with Type O. Since parents are ii, both must be carriers for i Mother must be IBi, Father must be IAi

Prob. of producing Type A = 0.25 Prob. of producing a daughter = 0.50 Therefore prob of producing Type A daughter must be found with the product rule…….. 0.25 ( 0.5) = 0.125 or 1/8 or 13% Diploma questions ask for answer rounded to 2 decimal places or to 2 significant digits

Genetics Problem Set www.biology.arizona

The Product Rule

Incomplete Dominance Codominance Intermediate Inheritance Cattle Snapdragons Red X White = Pink!! Blending occurs Codominance Cattle Red X White = Roan Both genes expressed White and red hair present

Gene for red (R) is incompletely dominant Red X White = Pink Gene for red (R) is incompletely dominant to gene for white (W)

Incomplete Dominance: Blending/3 distinct phenotypes

R R W W RW RW RW RW Phenotypes Genotypes All RW Predict the phenotypic outcome if a Red (RR) snapdragon is crossed with a White (WW) sd! R R Capital Letters used for both alleles since they are equally Dominant W RW RW W RW RW Phenotypes All pink! Genotypes All RW

R R R W RR RR RW RW Phenotypes Genotypes 2 RR : 2 RW Predict the phenotypic outcome if a red (RR) snapdragon is crossed with a pink (RW) sd! R R R RR RR W RW RW Phenotypes 2 Red : 2 pink Genotypes 2 RR : 2 RW

Intermediate? Or Co-dominant? Ask yourself does blending occur??

Predict the genotypes of the parents! Rr & Rr