Non-Mendelian Genetics Inheritance Concepts Mendel Never Imagined!

Mendelian Genetics (Complete Dominance) Only two possible Phenotypes: either dominant or recessive Tall plant X Short plant = Tall plant (TT) (tt) (Tt)

Non-Mendelian Genetics But, not all inheritance is based on the rules of Complete Dominance!!

Nonmendelian Genetics Introduction Mendelian Genetics describes inheritance patterns based on Complete Dominance or Recessiveness. There are other types of inheritance that Mendel never considered: Incomplete Inheritance Codominance Multiple Alleles Polygenic Traits Sex-linked Nonmendelian Genetics

Incomplete Inheritance The hybrid (heterozygous) offspring displays a THIRD Phenotype!! Neither trait is completely dominant, as a result, there appears to be a blending phenotype. Red Flower X White Flower = Pink (RR) (WW) (RW)

Incomplete Inheritance Problem What is the probability of pink flowers if pink flowers are bred with red flowers? R R 50% chance of Pink Flowers R RR RR W RW RW

Incomplete Inheritance Problem What is the probability of white flowers if pink flowers are bred with pink flowers?

CoDominance Both traits are dominant, and show up in the phenotype together. Co means “together” Black Cow X White Cow = Spotted Cow (BB) (WW) (BW)

Possible phenotypes are a black cow, 2 spotted cows, and a white cow CoDominance Problem What are all the possible phenotypes when two spotted cows are bred? B W Possible phenotypes are a black cow, 2 spotted cows, and a white cow B BB BW W BW WW

Below are imaginary organisms Below are imaginary organisms. Note horn shape, leg length, fur color and tail shape. Now determine the type of inheritance of the four traits by examining the genotypes of the parents and offspring.

Blood type displays both co-dominance and complete dominance Red Blood cells can either have a carbohydrate on their surface or not. The presence of a carbohydrate (I) is dominant to the absence of a carb (i). Additionally, there are two types of carbs that may exist on the surface of RBCs called A (IA) and B (IB). Cell surface carbs A and B are codominant, which means they could also show up at the same time on an RBC.

Blood Type Inheritance Rules: A person with the IA allele will have A carbohydrates. A person with the IB allele will have B carbohydrates. A person with the recessive i allele will have no carbohydrates. Or a person with both IA and IB alleles will have both A and B carbohydrates on their cells. Cells Genotypes Blood types IAi, IAIA Type A blood IBi, IBIB Type B blood IAIB Type AB blood ii Type O blood

Blood Type Problems IA IB i IA i IB i i IA i IB i If a woman with AB blood has children with a man who has type O, what will be the possible genotypes of their children? What will be their blood types? IA IB i IA i IB i i IA i IB i

Blood Type Problems Blood Type Problem 2: A woman with type B blood has a child with type O blood. How is this possible if her husband has type A blood?

Multiple Alleles When more than 2 varieties exist in a trait. Many animals have a variety of coat colors.

Polygenic Traits Require more than one gene (allele) to determine trait. Skin tone is determined by 4-6 genes—that means that there may be six different chromosomes involved!

Sex-linked Inheritance Genes for some traits are found on the sex chromosomes (X or y) Most of these traits are recessive the normal gene is dominant Heterozygous Females (XXc) are carriers. They do not show the trait, but carry a gene for the trait. Homozygous Females (XcXc) have the trait Males with the gene (XcY) have the trait.—They do not have another X to counterbalance the affected gene

Color blindness is a sex-linked recessive trait Color blindness is a sex-linked recessive trait. The gene for this trait is inherited through the X chromosome. If a woman with normal vision has children with a man who is colorblind, what are the chances that their children will be colorblind? Will any children be carriers of the trait? Xc Y X XXc XY XXc XY

Non-Mendelian Genetics What are the similarities and differences between each of these forms of inheritance? How will you remember? What are examples of each type? Incomplete inheritance CoDominance Multiple Alleles Polygenic Traits Sex-linked inheritance