When Heredity Follows Different Rules Chapter 12.2 pg 315-322 When Heredity Follows Different Rules

Up to now, every genetics problem we have done has fit this pattern Simple Mendelian Inheritance- trait with 2 alleles (one dominant and one recessive) Up to now, every genetics problem we have done has fit this pattern But………….

Things are about to Change!

Incomplete Dominance- heterozygous individuals show an intermediate phenotype

Incomplete Dominance RED Flower x WHITE Flower ---> PINK Flower

R = allele for red flowers W = allele for white flowers RW = genotype for pink flowers

Codominance equal expression of both alleles at the same time

Codominance Black x White --- Checkered

Codominant feather colors

R = allele for red feathers W = allele for white feathers RW = genotype for red and white feathers

Practice Problem (incomplete dominance) What would the genotypic and phenotypic ratios be of the offspring when crossing two pink flowers together?

Practice Problem (Codominance) What would the genotypic and phenotypic ratios be of the offspring when crossing checkered chickens together?

Practice Problem (incomplete dominance) What would be the result of crossing a homozygous white flower with a heterozygous pink flower?

Sex Determination 22 pairs of homologous chromosomes called Autosomes *remember: humans have 46 chromosomes 22 pairs of homologous chromosomes called Autosomes 1 pair of Sex Chromosomes XX = female, XY = male

Sex determination

Sex-Linked Inheritance Traits that are located on a sex chromosome (x or y) Will affect a certain sex more often

Sex-linked example b = bald B = not bald

Polygenic Inheritance Trait controlled by many genes (more than 2) Gives a wide range of traits Example genotype: AaBBCCDd

Polygenic Inheritance

Multiple Alleles Trait controlled by more than 2 alleles of a single gene

BA: Ash Red, B: Blue, b: Chocolate Multiple Alleles Example: Feather color in pigeons BA: Ash Red, B: Blue, b: Chocolate

BA: Ash Red

B: Blue

b: Chocolate

Human blood type: codominance and multiple alleles

A B AB IAIB IBIBor IBi IAIA or IA i A and B None Genotypes Surface Molecules Phenotypes IAIA or IA i A IBIBor IBi B IAIB A and B AB ii None O

Practice Problem (Codominance and multiple alleles) A man who is type A is accused of fathering 2 children. One of the kids has type O blood and the other has type B. The mother has type B. Could this man be the father of both children? Prove your answer using punnett squares.