If the curve shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations, then which of these is (are) probably occurring?

#Question id: 9050

#Unit 9. Diversity of Life Forms

If an ecologist were studying the regional interactions among multiple populations of different species and how they influence the exchange of materials between their various environments, then this would be an example of which kind of research?

#Question id: 3697

#Unit 3. Fundamental Processes

In the Meselson-Stahl DNA replication experiment, what percent of the DNA was composed of one light strand and one heavy strand after one generation of growth in 14N containing growth media?

#Question id: 24221

#Unit 1. Molecules and their Interaction Relevant to Biology

#Question id: 420

#Unit 1. Molecules and their Interaction Relevant to Biology

The structure of NAD+ does not include:

#Question id: 723

#Unit 1. Molecules and their Interaction Relevant to Biology

Common structural elements in proteins such as α-helices or β-sheets are characterized by uniformly repeating, energetically favorable main chain conformations which additionally exhibit a completely saturated hydrogen-bonding network of the main chain NH and CO groups. Although polyproline or polyglycine type II helices (PPII or PGII ) are frequently found in proteins, they are not considered as equivalent secondary structure elements. Which of the following statements are correct about PP and PGs.

A. PGII -like helices form hexagonal bundles which appear to fulfill the criterion of a (largely) saturated hydrogen-bonding network of the main-chain groups

B. main chain NH and CO groups of the central PGII -helix are saturated by either intra- or intermolecular hydrogen-bonds, resulting in a self-contained hydrogen-bonding network

C. The formation of the right-handed PPI helix is possible only with proline residues because of the required cis conformation. 

D. PPII helices seem to be stabilized by main chain-water hydrogen bonds (in the absence of main chain- main chain H-bonds), and tend to have a regular pattern of hydrogen bonds with water. After this, it is not surprising, that PPII helices are found mostly on the protein surface.