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.