Blood Types and Skin Colors Incomplete Dominance and Co-Dominance

Non-Mendelian Inheritance Multiple alleles = trait is determined by more than two alleles (ex. Human blood types) Polygenic traits = trait influenced by several genes (ex. Human eye color, weight, skin tone) Incomplete dominance = one allele is not completely dominant over the other and the two phenotypes blend together in the heterozygote (Ex: flowers…red, white, pink) Co-dominance= both alleles for a gene are expressed when present in the heterozygote (Ex: cattle…red, white, roan coat)

Example 1: Flowers Example: Snapdragons can be red, white, or pink (heterozygous). Incomplete dominance - neither allele is dominant, red x white = pink Use all capital letters - Red (RR) x White (WW) = Pink (RW) What traits followed this one in the “Making Faces” lab? Hair color, skin color, eye color, mouth size, eye distance, hair texture

Example 2: Fish Coloration Co-Dominance- both alleles are expressed in the heterozygote In a certain fish, blue scales and red scales are co-dominant. When a fish has the genotype B R, it has a patchwork of blue and red scales. What happens if you breed this fish with a fish that only has Blue Scales?

Example 2: Fish Coloration  Step 1: Determine the genotypes of the parents RR = Red, BB = Blue, RB = patchwork fish Step 2: Set up the Square Step 3: Count the number of each phenotype: 1/2 will by patchwork 1/2 will be blue

Fish Coloration Practice What happens when you cross two patchwork fish? (Draw the Punnett square, list phenotypes and percentages of each)

Special Inheritance: Human Blood Types 1901 - Austrian Karl Landsteiner discovered human blood groups Even animals have blood types

Blood Type is Controlled by 3 Alleles 4 Possible Blood Types Alleles: IA, IB, i Special Inheritance: IA & IB are co-dominant i (type O allele) is recessive Phenotype Genotype(s) Type A blood IAIA or IAi Type B blood IBIB or IBi Type AB blood IAIB Type O blood ii

Genotypes & Phenotypes

Blood Type Antigens

Blood that has antibodies on it that is not recognized by the body will be attacked by your immune system AB is the Universal Acceptor – it has no anti-A or anti-B antigens O Is the Universal Donor – it has not A or B antibodies and cannot be attacked

Consider Both Parents Type A (genotype IAIA) x Type O (genotype ii)

Rh Factor A person can either be Rh + or Rh – (positive is dominant)

Rh Factor and Pregnancy *Problem: When a fetus is Rh+ and the mother is Rh-, this can cause the mother’s immune system to attack the fetus. There are drugs that will suppress this. reaction.

Blood Type Test

Classwork Answer questions 1-8 on your own! Please ask me for help as needed The unfinished questions will be homework

Punnett Square Strategy Read the question Pick out the traits and dominant / recessive (underline) Find information about the parents (circle) Write down the letters and what they stand for (Capital letter = dominant) Write down the parents’ genotype If two traits, FOIL to get all possible combination Complete the Punnett square Choose the right size (2x2 or 4x4) Put the parents’ genes on the outside Combine the genes in the boxes Interpret the Punnett square Answer the question Circle your answer

Punnett Square Strategy Read the problem. Look for: The dominant & recessive trait (with letters, sometimes) Information about the parents Write down our allele letters & what they stand for (ex: f = faint, F = not fainting) Write out the parents’ genotypes If it’s a two gene cross, FOIL to get all of the possible combinations Make and solve the Punnett square Choose the right size (2x2 or 4x4) Put the parents’ genes on each side Cross the traits Interpret the Punnett square See what the question is asking for Circle your answer