Download The ability to roll the tongue is dominant over the inability to do so in

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.