Genetic Puzzle
Are your earlobes free hanging or attached to your head?
Some people have earlobes than hang, and some people don’t. The gene for free hanging earlobes is dominant,
and the gene for attached earlobes is recessive. That means that you have free hanging earlobes if you inherited
the gene for it from at least one of your parents meaning that your genotype is “EE” (both genes for freehanging lobes) or “Ee” (one gene for free hanging lobes). However, you have attached earlobes if you inherited
genes from both parents that give instructions for attached lobes (“ee”).
Can you figure out these people’s genotypes (what the genes are) based on the phenotype information (whether
or not they have free hanging lobes) and genetic relationships described below?
Solve the puzzle!
Clues:
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Mary is the only one in her immediate family who has attached lobes.
Both of Mary's parents have free hanging lobes.
Mary's brother Fred also has free hanging lobes.
Questions:
1. If Mary has attached lobes, what must her genotype be?
2. If both Mary’s parents have free hanging earlobes, but they had a daughter who has attached lobes, what must
their genotypes be?
3. What are the possible genotypes for Fred, Mary’s brother? Is it possible to identify his exact genotype?
4. Can you draw a pedigree using the following key?