#Question id: 752
#Unit 1. Molecules and their Interaction Relevant to Biology
The A260/A280 ratio of a double-stranded DNA sample can be used to assess its purity. The value for the pure DNA is ----------------
#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.
#Question id: 23353
#General Aptitude
#Question id: 23148
#Unit 13. Methods in Biology
#Question id: 1521
#Unit 4. Cell Communication and Cell Signaling
we examine how the deregulation of growth-promoting and growth-inhibiting signaling pathways contributes to tumorigenesis. Mutations-
A. A mutation that alters a single amino acid (valine to glutamine) in the transmembrane region of the HER2 receptor
B. A deletion that causes loss of the extracellular ligand-binding domain in the EGF receptor Results-
i. dimerization of the receptor, even in the absence of the normal EGF-related ligand, transforming it into the oncoprotein, a constitutively active kinase
ii. to constitutive activation of the kinase activity of the resulting oncoprotein
iii. no dimerization, even in the presence of the normal EGF-related ligand, repression of kinase activity
which of the following results are displayed after these mutations?