Ch.11-3 Non-Mendelian Inheritance I

POINT > Describe other patterns of inheritance POINT > Define different allele representation POINT > Describe incomplete dominance POINT > Describe codominance POINT > Define polygenic inheritance POINT > Describe examples of environmental influence

The mono- and dihybrid crosses we’ve studied represent “simple” inheritance: dominant and recessive alleles and only 1 gene per trait Most traits do not show simple inheritance Most alleles are not completely dominant/recessive Usually more than just two alleles for a given gene (an individual has two, but the population has others) Most traits are controlled by more than one gene

We represent alleles slightly differently: the trait is expressed as a single capital letter (ex. Color would be ‘C’) Specific alleles are represented by superscript letters (ex. Red color would be ‘C R ’ / White color would be ‘C W ’)

WB CHECK: Which statement is true? a) Most genes have two alleles b) Most traits are controlled by one gene c) One organism has two alleles for each gene d) Most alleles are either dominant or recessive

WB CHECK: The 9:3:3:1 phenotype ratio shows up a) in the F 1 of a monohybrid cross b) in the F 1 of a dihybrid cross c) in the F 2 of a monohybrid cross d) in the F 2 of a dihybrid cross

Incomplete dominance: The heterozygous phenotype is a blend between the two homozygous phenotypes Neither allele is fully dominant nor recessive

Ex. Snapdragon Flowers

P cross Genotype 100% C R C W CRCR CRCR CWCW CWCW C R C W Phenotype 100% Pink 4 C R C W : 0 4 Pink : 0

F 1 cross Genotype CRCR CWCW CRCR CWCW C R 25% C R C R 50% C R C W 25% C W C W C R C W C W 1 : 2 : 1

F 1 cross Phenotype 25% Red 50% Pink 25% White 1 : 2 : 1 C R C R C W C W CRCR CWCW CRCR CWCW

Codominance: Both alleles are fully & separately expressed Neither allele is dominant over the other

Ex. Shorthorn Cattle: Differences in hair color Red Hair (homozygous C R C R )

Ex. S horthorn Cattle Differences in hair color White Hair (homozygous C W C W )

Ex. Shorthorn Cattle Differences in hair color Roan Hair (heterozygous C R C W )

P cross Genotype 100% C R C W CRCR CRCR CWCW CWCW C R C W Phenotype 100% Roan 4 C R C W : 0 4 Roan: 0

F 1 cross Genotype CRCR CWCW CRCR CWCW C R 25% C R C R 50% C R C W 25% C W C W C R C W C W 1 : 2 : 1

F 1 cross Phenotype 25% Red 50% Roan 25% White 1 : 2 : 1 C R C R C W C W CRCR CWCW CRCR CWCW

WB CHECK: A tall corn plant is crossed with a short corn plant. The height of the offspring is intermediate between the parents height. This is an example of a) simple Mendelian inheritance b) codominance c) incomplete dominance d) mutation

WB CHECK: A ferret with black fur is crossed with a ferret with brown fur. The offspring have fur that has patches of black and brown fur. This is an example of a) simple Mendelian inheritance b) codominance c) incomplete dominance d) mutation

Ex. ABO Blood Groups Different alleles represent different antigens on the surface of red blood cells There are three alleles: I A I B i

ABO Blood Groups: Blood Type A A-type antigens

ABO Blood Groups: Blood Type B B-type antigens

ABO Blood Groups: Blood Type AB A & B antigens

ABO Blood Groups: Blood Type O Recessive Allele - Neither antigen present

Genotype Phenotype  Blood Type A   Blood Type B   Blood Type AB   Blood Type O  I A I A or I A i I B I B or I B i IAIBIAIB i A B AB O We use the letter “I” for blood genotypes

WB CHECK: One parent is a blood type A heterozygote, and the other parent is a blood type B heterozygote. Draw a Punnett square to show the potential offspring. What percent of offspring will have type O blood?

IAIA i IBIB i IAIBIAIB IBiIBi I A ii Genotypes 25% I A i 25% I B i 25% I A I B 25% i i 1 : 1 : 1 : 1

IAIA i IBIB i IAIBIAIB IBiIBi I A ii Phenotypes 25% A 25% B 25% AB 25% O 1 : 1 : 1 : 1 i ii

Polygenic traits are controlled by two or more genes Ex. Skin Color: at least 5-6 genes Ex. Eye Color: 6-15 genes involved A majority of traits fall under this category

Environmental conditions can affect gene expression (phenotype) by influencing genetically determined traits Doesn’t change genotype, just the expression

Ex. Hydrangea Flower color changes depending on pH (aluminum + more acidic = bluer)

Ex. Arctic Hare Coat color changes based on season (amount of light, snow, temp)

Read pages Assess page 321 #1-2 Punnett Square WS