Mutations occur at the same rate in both exons and introns, but 

a) If unwanted mutations occur at exons they are conserved more effectively by selection

b) Exons are negatively selected when undergo mutation

c) Introns may more freely accumulate point substitutions and other changes due to no selection pressure. 

d) exon mutations are eliminated more effectively by selection.

Which of the above is true regarding introns and exons 

#Question id: 3993

#Unit 3. Fundamental Processes

An example of coordinate control is the down-regulation of ribosomal RNA synthesis in response to amino acid starvation, which will cause synthesis of ribosomal proteins to be limited.  What is the correct order of the following events that participate in the signaling process?

1. Binding of stringent factor to the ribosome.

2. Formation of the unusual nucleotide ppGpp.

3. Formation of the unusual nucleotide pppGpp.

4. Uncharged tRNA binds in the ribosomal A-site.

#Question id: 2582

#Unit 2. Cellular Organization

Following statements are regarding to dynamics of actin filaments.

A. When the concentration of G-actin is above the Cc, the filament end will grow; when it is less than the Cc, the filament will shrink.

B. ATP–G-actin is added much faster at the (+) end than at the (−) end, resulting in a lower critical concentration at the (+) end than at the (−) end.

C. At steady state, actin subunits treadmill through a filament. ATP-actin is added at the (+) end, ATP is then hydrolyzed to ADP and Pi, Pi is lost, and ADP-actin dissociates from the (−) end.

D. ATP–G-actin is added much faster at the (-) end than at the (+) end, resulting in a lower critical concentration at the (-) end than at the (+) end.

E. At steady state, actin subunits treadmill through a filament. ATP-actin is added at the (-) end, ATP is then hydrolyzed to ADP and Pi, Pi is lost, and ADP-actin dissociates from the (+) end.

Which of the following statements are correct?

#Question id: 27135

#Unit 7. System Physiology – Animal

#Question id: 11873

#General Aptitude

#Question id: 12961

#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 data in the table indicate which of the following?