Pedigree charts are powerful visual tools used by geneticists to trace the inheritance of specific traits through generations. When combined with the ABO and Rh blood typing systems, pedigrees become engaging, real-world puzzles for biology students.
Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring.
After solving the blood type puzzle, introduce a fake gel electrophoresis result for an STR (short tandem repeat) marker. This teaches that blood typing is probabilistic (excludes only, doesn’t confirm 100%), while DNA is individualizing.
Rather than a single linear path to the answer, the updated key presents branching logic. For example: “Claimant 1 has type O blood. Could they be the child of a type AB parent and a type A parent? No, because AB × A can never produce type O (which requires two i alleles).” This approach trains students in hypothesis testing. lab activity blood type pedigree mystery answer key upd
| Step | Action | Key Insight | | :--- | :--- | :--- | | 1 | Draw the basic family structure. | Visualizes all relationships at a glance. | | 2 | Fill in all known blood types (e.g., A, B, O). | This is the raw data you must work with. | | 3 | Infer possible genotypes (e.g., IAi , IBi , ii ). | Use the rules of inheritance to go deeper than just the phenotype. | | 4 | Eliminate individuals who don't match the crime scene blood type (e.g., not Type A). | Narrows the suspect pool significantly. | | 5 | Shade individuals with the recessive attached earlobe trait. | Prepares for final elimination round. | | 6 | Identify the remaining suspect who has Type A blood and attached earlobes. | This is the thief. |
may have stolen the money to provide for his children or because he discovered that Alexandria
In rare clinical cases, individuals may possess the genes for Type A, B, or AB blood but test as Type O. This is known as the Bombay Phenotype. It occurs when a person lacks the H substance , a foundational molecular structure required for A and B antigens to attach to red blood cells. In advanced lab activities, this serves as an excellent example of epistasis. Pedigree charts are powerful visual tools used by
Any relative with Type B, Type AB, or Type O blood is excluded if the evidence is Type A. Final Identification:
: If the blood types of the parents are known, their genotypes can be inferred. For example, if a parent has Type A blood, they could be either AA or AO.
The patriarch, Arthur Montgomery, was an uncompromising man with blood type A. His wife, Eleanor, possessed the rare and elusive blood type O. By all the laws of basic Mendelian genetics, their children should have been either type A or type O. Yet, their youngest daughter, Clara, was sitting in the clinic with a confirmed blood type of AB. After solving the blood type puzzle, introduce a
: While several family members have Type A blood or attached earlobes, is the only one who possesses both traits simultaneously.
The mystery unfolds when the family lawyer arrives to read Joseph’s will, only to discover that a sum of money—equal to one person’s share of the estate—has been stolen from a safe. The only clues are a trail of on the safe door and a witness statement from the maid, who saw a masked figure with attached earlobes fleeing the scene.