Quiz Genetics
1)In cats the gene for short hair is dominant over the gene for long hair (angora). A short–
haired tom is mated with an Angora female. She bears eight kittens, six short–haired and
two with long hair. How do these numbers compare with the expected ratio? If you mated
these same cats four more times and obtained a total of forty offspring, would you expect
the results to be a closed approximation of the expected ratios? Explain.
2)In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on. This can be tested by breeding the dog to a deaf female (dd). Draw the Punnett squares to illustrate these two possible crosses. In each case, what percentage/how many of the offspring would be expected to be hearing? deaf? How could you tell the genotype of this male dog? Also, using Punnett square(s), show how two hearing dogs could produce deaf offspring.
3)List all the possible genotypes for each of the 4 blood types:
Type O______
Type A______
Type B______
Type AB______
A woman with type A blood (genotype: AO) is married to a type B person (genotype: BO). What blood types will their children have?
4)Some dogs bark while trailing, others are silent. The barking trait is due to a dominant gene. Erect ears are dominant to drooping ears. What kind of pups would be expected from a double heterozygous erect–eared, barker mated to a drooped–eared, silent trailer? Gene B controls the barking ability; gene E controls ear shape.
Let B be the dominant allele for the barking trait.
Let b be the recessive allele for the silent trait.
Let E be the dominant for erect ears.
Let e be the recessive allele for drooping ears.
5)There is another gene that codes for another, different antigen that also occurs on the surface of our RBCs, and technically, that gene also has multiple alleles. However, most people either have or do not have one particular allele called the “d” allele. This gene codes for an antigen that is called “Rh factor” because it was first discovered in Rhesus monkeys. People who have instructions to “make d antigen” are referred to as Rh+ (the allele is often symbolized by the letter “R”), while those who have “I don’t know how to make d antigen” instructions are called Rh– (the allele can be symbolized by “r”). Since this is a totally separate gene than the ABO blood group, if you’re doing a genetic cross that involves both ABO andRh, that would be a dihybrid cross.
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Ms. Branch, Ms. Davis, and Ms. Rucker all entered the same hospital and gave birth to baby girls on the same day, and all three babies were taken to the nursery to receive care, there. Someone later claimed that the hospital mixed up the babies. As a hospital administrator, it is your job to make sure that each pair of parents has the correct baby, so you order blood typing to be done on all the parents and all the babies. Here are the results:
Person / Blood Type(Phenotype)
Ms. Branch / A+
Mr. Branch / B+
Ms. Davis / B–
Mr. Davis / O+
Ms. Rucker / A+
Mr. Rucker / A–
Baby A / O+
Baby B / AB–
Baby C / B–
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Which baby belongs to which couple?