Chapter 4 Genetics
exam questions and
answers
13.) The A locus and the D locus are so tightly linked that no
recombination is ever observed between them. If Ad/Ad is crossed
with aD/aD and the F1 is intercrossed, what phenotypes will be seen
in the F2 and in what proportions - answer P: Ad/Ad x aD/aD
F1: Ad/ aD
F2: 1 Ad/Ad Phenotype Ad
2 Ad/aD Phenotype AD
1 aD/aD Phenotype aD
16.) A strain of Neurospora with the genotype H*I is crossed with a
strain with the genotype h*i. Half the progeny are H*I, and the other
half are h*i. Explain how this outcome is possible. - answer
Because only parental genotypes are recovered, the two genes must
be tightly linked and recombination must be vary rare. Knowing how
many progeny were looked at would give an indication of how close
the genes are.
27) The mother of a family with 10 children has blood type Rh+. She
also has a very rare condition (elliptocytosis, phenotype E) that
causes red blood cells to be oval rather than round in shape but that
produces no adverse clinical effects. The father is Rh- and has
normal red blood cells. The children are 1 Rh+e, 4Rh+E, and 5 Rh-e.
The mothers parents who are Rh+E and Rh-e. One of the 10 marries
someone who is Rh+ e and they have an Rh+E child.
exam questions and
answers
13.) The A locus and the D locus are so tightly linked that no
recombination is ever observed between them. If Ad/Ad is crossed
with aD/aD and the F1 is intercrossed, what phenotypes will be seen
in the F2 and in what proportions - answer P: Ad/Ad x aD/aD
F1: Ad/ aD
F2: 1 Ad/Ad Phenotype Ad
2 Ad/aD Phenotype AD
1 aD/aD Phenotype aD
16.) A strain of Neurospora with the genotype H*I is crossed with a
strain with the genotype h*i. Half the progeny are H*I, and the other
half are h*i. Explain how this outcome is possible. - answer
Because only parental genotypes are recovered, the two genes must
be tightly linked and recombination must be vary rare. Knowing how
many progeny were looked at would give an indication of how close
the genes are.
27) The mother of a family with 10 children has blood type Rh+. She
also has a very rare condition (elliptocytosis, phenotype E) that
causes red blood cells to be oval rather than round in shape but that
produces no adverse clinical effects. The father is Rh- and has
normal red blood cells. The children are 1 Rh+e, 4Rh+E, and 5 Rh-e.
The mothers parents who are Rh+E and Rh-e. One of the 10 marries
someone who is Rh+ e and they have an Rh+E child.
