Description
GENETIC PROBLEMS
Work to solve the genetics problems on this worksheet). For most questions you will need to
draw a Punnett square and provide a written explanation.
1. To solve these two Punnett Squares on blood types, use the following chart for
reference:
(The chart is inheritance of the ABO blood system in humans)
a. Jane and her husband are both type AB. Could they have a type O daughter?
Draw a Punnett square to support your explanation.
b. An archaeologist discovers an unopened tomb in Egypt. Inside the tomb, he finds
the mummies of two adults and two children. Inscriptions identify the two adults
as the Chief Scribe and his wife. The inscriptions tell how their and son and his
best friend drowned in the Nile River when their boat overturned. The mummies
are so well preserved that lab technicians are able to type their blood. Both
adults are type B. Child 1 is type O, Child 2 is type B. Can you definitively
determine which one is their son? Why or why not?
2. In humans, the allele for albinism is recessive to the allele for normal skin pigmentation.
What is the Punnett square and probability that a child of a heterozygous mother and
father will be an albino?
3. Among Hereford cattle there is a dominant allele called polled; the individuals that have
this allele lack horns. After college, you acquire a herd consisting entirely of polled
cattle, and carefully determine that no cow in the herd has horns. Among the calves
born that year, however, some grow horns. You remove them from the herd and make
certain that no horned adult has gotten into your pasture. Despite your efforts, more
horned calves are born next year. What is the reason for the appearance of the horned
calves? If your goal is to maintain a herd consisting entirely of polled cattle, what should
you do? Use a Punnett Square to defend you answer.
4. Duchene’s Muscular Dystrophy (DMD) is a severe disorder that results in degeneration
of skeletal muscle tissue. Affected individuals typically do not survive past their late
twenties. The disorder is caused by a mutation in the dystrophin gene on the
X-chromosome. The disorder primarily affects males. Males who have the condition are
very unlikely to have children of their own. Females are very rarely affected by the
mutation, but they may carry it. Draw a Punnett square that reflects the most likely
scenario for how a healthy couple could produce a child with DMD. What gender among
the offspring is affected and why?
5. At one gene location on a human chromosome, a dominant allele controls whether you
can curl the side of your tongue upward. People homozygous for the recessive allele
cannot roll their tongue. At a different location, a dominant allele controls whether
earlobes are attached or detached (dominant trait). These two gene pairs assort
independently.
So, suppose a tongue-rolling woman with detached earlobes marries a man who has
attached earlobes and can’t roll his tongue. Their first child has attached earlobes and
can’t roll his tongue.
a. What are the genotypes of the mother, father, and child?
b. What is the probability that a second child will have detached earlobes and won’t
be a tongue roller? Draw a Punnett square to support your answer.
6. In Jimson weed, the allele that produces violet petals is dominant over that for white
petals, and the allele that produces prickly capsules is dominant over that for smooth
capsules. A plant with white petals and prickly capsules was crossed with one that had
violet petals and smooth capsules. The F1 generation was composed of 47 plants with
white petals and prickly capsules, 45 plants with white petals and smooth capsules, 50
plants with violet petals and prickly capsules, and 46 plants with violet petals and
smooth capsules. What were the genotypes of the parents? Draw a Punnett square to
support your answer
