Genetics Continued... Incomplete Dominance and Codominance

Essential Question: How can more complex traits be inherited and expressed in ways other than complete dominance?

Incomplete Dominance Incomplete dominance occurs when one trait is not fully dominant over the other trait. What would a heterozygous individual look like in this case? The heterozygous phenotype is a mixture of both phenotypes.

Codominance Codominance occurs when one trait is not fully dominant over the other trait. What would a heterozygous individual look like in this case? In the heterozygous situation, BOTH traits are expressed at the same time.

Because neither allele is dominant or recessive, both alleles are written as capital letters, but using two different letters.

Blood Types

There are three alleles in blood types and these alleles are codominant. Alleles: A, B, O Blood types: A, B, AB, O

Blood type alleles determine the proteins on the membrane of the blood cells. Antigens – the proteins on the surface of the blood cell A person has antibodies to fight off any proteins that their blood does not contain.

Blood types are determined by mixing blood samples with antibodies for each blood type. If the blood agglutinates (clumps), then that blood type is present. Example: Type A antibody is mixed with the blood and it agglutinates, what blood type(s) could it be? A or AB

Rh Factor Rh is another protein on the surface of blood cells. It is controlled by a separate gene. Rh is written as either + or –

You can donate blood to someone with the same proteins or more proteins. You can receive blood with the same proteins or fewer proteins.

Blood Type Facts NFO/bloodtype.html

CSI: Tucson Date: January 16, 2013 Time: 9:48pm Location: Tucson Mall parking lot Event Description: A witness called police and reported seeing a fight in a Tucson Mall parking lot. The witness gave vague details because it was dark outside and the lights in the parking lot were broken. The witness claims to have seen two men in a violent fight or struggle in the parking lot. Both men appeared to be injured and the fight ended with one man falling to the ground and the other man taking something from him and running away. At this time, the witness reportedly ran away so as not to be seen by either assailant.

When police reported to the scene, they did not find any victim, witness, or assailant. The only evidence found at the scene was blood on the asphalt. From further investigation, police came up with two possible suspects for the assailants in the fight. The parents of both suspects are willing to give blood samples to prove the innocence of their sons. Testing will be done to determine the blood types of the blood found at the scene and of the parents.

Test Results: Two blood types were found at the scene. Blood Sample #1: Agglutination with both anti-A antiserum and anti-B antiserum Blood Sample #2: Agglutination with anti-A antiserum only Parents of Suspect 1: Mother: heterozygous B Father: Type O Parents of Suspect 2: Mother: AB Father: Homozygous A

Question: Which suspect was involved in the crime? Conclusion: Answer the question using complete sentences. Back up your answer by telling what blood types were found at the scene and explain how you are able to determine which suspect the blood belongs to.