You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium.

Next, you isolate a third mutant, MelC–, which gives constitutive melibiase expression. The MelC– mutation is closely linked to Mel1 and MelB–. Genetic tests of the MelC– mutation yield the following:

 

As above, classify the MelC– mutation in terms of its basic genetic properties and explain how you arrived at your conclusions.

#Question id: 12753

#Unit 13. Methods in Biology

#Question id: 12754

#Unit 13. Methods in Biology

#Question id: 12755

#Unit 10. Ecological Principles

#Question id: 12756

#Unit 10. Ecological Principles

Flycatcher birds that migrate from Africa to Europe feed their nestlings mostly with moth caterpillars. The data presented show the mean dates of egg laying, hatching, and fledging of flycatcher young, and the 1980 and 2000 peak mass of caterpillars.

The most likely cause for the shift in caterpillar peak mass is

#Question id: 12757

#Unit 10. Ecological Principles

#Question id: 12758

#Unit 10. Ecological Principles

Refer to the following experiment, which is designed to test the co evolutionary relationships among an unpalatable butterfly (the  monarch),  a  palatable  butterfly  (the  viceroy),  and  a  butterfly  predator  (the  jay).  Monarch butterflies are reared on three diets: milkweed (their natural food), cabbage, and cabbage treated with an extract from milkweed leaves. Viceroy butterflies, mimics of monarchs, also are reared on three diets: willows (their natural food), cabbage, and cabbage treated with an extract from milkweed leaves. In trial 1 of the first experiment, adult butterflies reared on a particular diet are presented one at a  time  at  1-hour  intervals  to  jays  and  the  jays  are  allowed  to  feed.  Each jay is  fed  until  it refuses to eat the butterfly presented, but no more than 12 butterflies are presented to a jay during a particular test. Five birds are used for each test; therefore, up to 60 butterflies can be consumed for each diet test. The observer records the actual number of butterflies  eaten. In trial 2, the experiment is repeated 2 weeks later. In the second experiment, the butterflies are reared on the same diets as in experiment 1. However, when they are offered to jays, some jays receive a monarch  reared  on  milkweed  before  being  offered  the  butterflies  reared  on  the  experimental  diets;  the  other  group  of jays is  first given a viceroy reared on willow before being  offered the butterflies reared on the experimental diets. The initial butterfly offered is included in the total number eaten, but no more than 12 butterflies are presented to each jay.

The experimental design and the data indicate which of the following about the jays?