When the hybrid offspring shows an intermediate phenotype between the two parents. Example: Flower color C R C R = red C W C W = white C R C W = pink

High Cholesterol- LL= normal Cholesterol LL’= High Cholesterol L’L’ = Very High Cholesterol R3s See Cholesterol Worksheet for info and Punnett Squares.

When the hybrid offspring shows both parental traits. Example: Roan Coat Color in horses RR = red R’R’ = white RR’ = roan (has both red and white hairs).

An inherited disease where people who have the allele for sickle cell have defective hemoglobin, causing misshaped blood cells that do not carry enough oxygen. In the heterozygous form, the disease causes anemia and pain, but also provides a tolerance to malaria. c3hUhhyc c3hUhhyc In the homozygous form, the disease can cause organ failure and death. Sickle Cell Anemia (codominance in humans)

The change in shape occurs in the body’s narrow capillaries after the hemoglobin delivers oxygen to the cells. Sickle-cell anemia Normal red blood cell Sickle cell

Sickle-cell anemia Abnormally shaped blood cells, slow blood flow, block small vessels, and result in tissue damage and pain. Normal red blood cell Sickle cell

AA= normal AS= mild anemia- some sickle cells, some normal- resist malaria infection SS= disease, anemia, organ damage

What is the probability that a baby will have full blown sickle cell disease if both parents have mild sickle cell anemia?

AS AAAAS S SS 25% chance of SS

Mendel’s laws of heredity also can be applied to traits that have more than two alleles. Multiple Alleles Govern Blood Type The ABO blood group is a classic example of a single gene that has multiple alleles in humans.

Multiple Alleles Govern Blood Type Human Blood Types l A l A or l A li l B l B or l B i lA lBlA lB ii Genotypes Surface Molecules Phenotypes A B A and B None A B AB O

The gene for blood type, gene l, codes for a molecule that attaches to a membrane protein found on the surface of red blood cells. The ABO Blood Group The l A and l B alleles each code for a different molecule. Your immune system recognizes the red blood cells as belonging to you. If cells with a different surface molecule enter your body, your immune system will attack them.

The l A allele is dominant to i, so inheriting either the l A i alleles or the l A l A alleles from both parents will give you type A blood. Phenotype A: Blood type A Surface molecule A is produced. Surface molecule A

The l B allele is also dominant to i. Phenotype B: Blood type B To have type B blood, you must inherit the l B allele from one parent and either another l B allele or the i allele from the other. Surface molecule B is produced. Surface molecule B

The l A and l B alleles are codominant. Phenotype AB: Blood type AB This means that if you inherit the l A allele from one parent and the l B allele from the other, your red blood cells will produce both surface molecules and you will have type AB blood. Surface molecule B Surface molecule A

The i allele is recessive and produces no surface molecules. Phenotype O: Blood type O Therefore, if you are homozygous ii, your blood cells have no surface molecules and you have blood type O.

Determining blood type is necessary before a person can receive a blood transfusion because the red blood cells of incompatible blood types could clump together, causing death. The importance of blood typing

Blood type A Blood cells have surface protein A

Blood type B Blood cells have surface protein B

Blood type AB Blood cells have surface proteins A and B

Blood type O Blood cells have no surface proteins