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Genetics Problems: Human Traits Name: Directions: Answer the following questions about Simple Dominance. 1. The ability to roll the tongue is dominant (T) over the inability to do so (t). a. If two heterozygous tongue-rollers have children, what genotypes could their children have? http://www.ncrtec.org/tl/camp/gene/curl.htm b. If a non-tongue-roller has children with a homozygous tongue-roller, what will their children's genotypes be? 2. One type of color blindness (website with more information) prevents people from clearly detecting green objects. This trait results from a recessive allele. Use a Punnett Square to predict the phenotypic results of a cross between a man with this type of color blindness and a woman heterozygous for the trait. (Note, assume it is not linked on the X chromosome – although many are.) 3. Albinism is a recessive trait (website with more information). a. If an albino female marries a normally pigmented man and their first child is albino, what are their genotypes? and b. What is their child’s genotype? 4. Eye color is controlled by many genes, however, if we only examine brown eyes versus blue eyes, use a Punnett square to explain how two brown eyed people could have a blue eyed child. (For more information on eye color visit this website.) 5. The ability to taste PTC (website with more information) is due to a dominant trait. Create a Punnett square for a man who is a taster and a woman who is a non-taster. Assume that the father’s mother was a non-taster. 6. In humans, the allele for six fingers (F) is dominant to the allele for five fingers (f). (See Wikipedia Commons image) If both parents are heterozygous for six fingers, what is the probability that their first child will be “normal” (have five fingers)? 7. See image of earlobe types at this website. Alvin has free earlobes (caused by a dominant gene) and is unable to taste PTC (the ability to taste is dominant). Alvin’s father had attached earlobes. Alvin marries Katrina who has free earlobes and is a taster (she is homozygous for both traits). a. What is Alvin’s genotype for earlobes? What is Alvin’s genotype for PTC tasting? b. What is Katrina’s genotype for earlobes? What is Katrina’s genotype for PTC tasting? c. Will all of their children be tasters? d. Will the children all have free earlobes? e. Could they expect a child with attached earlobes who is a taster? 8. The widow's peak is caused by a dominant trait. If a male who is heterozygous for widow's peak marries a woman who is homozygous recessive for no widow's peak, then what is the probability of their offspring inheriting the widow's peak? 9. In the Andalusian fowl, a single pair of alleles controls the color of the feathers. Three colors are observed, blue, black, and splashed white. Crosses among these three types yield the following results. Parents Offspring Black x splashed white Blue Black x black Black Black x blue Blue and black (1:1) Blue x splashed white Blue and splashed white (1:1) Splashed white and splashed white Splashed white a. What type of gene inheritance pattern is this? b. What would be the phenotypic ratio of the offspring from a cross between a blue fowl and blue fowl? Show a Punnett Square to explain your answer. : c. If you wanted to sell eggs, all of which would yield blue fowl, how should you proceed? Information about other human traits 10. Determine what your genotype is for different traits. Go to this website and ask your parents what their phenotype is. 11. Hair type 12. Double jointed thumb (which can be considered an example of ‘hypermobility’ not really ‘double joints’) 13. Hitch hiker’s thumb (pictured at this website along with several other traits) 14. Dimples and chin clefts 15. Other types of tasting: sodium benzoate. Could sensitivity to PTC and/or thiourea (another type of taste strip you may try) cause children to dislike broccoli, brussel sprouts or cabbage (aka, cruciferous vegetables)? Check out this website. 16. Pinky Fingers 17. Interlocking Hands (termed ‘hand fold’ on this website) 18. Inheritance of several human traits as well as some genetic diseases.