Question

Q2 An E. coli culture growing on a lactose supplemented media does not produce any β-galactosidase. Identify the incorrect statement.

a. The E. coli could be a lacZ mutant

b. The E. coli may have a mutated LacI protein that cannot bind to the operator

c. The E. coli may have a mutated LacI protein that cannot bind to the inducer

d. The growth medium may have a high amount of glucose

e. The E. coli may have a mutated lacO that does not allow repressor binding

Q3 Identify the false statement from studies of development in Drosophila.

a. Homeotic genes are responsible for the development of segments in Drosophila.

b. The 180 bp region of homology in homeotic genes is called a homeobox.

c. The homeobox codes for a DNA binding domain.

d. The polycomb group of proteins are involved in silencing of hox genes.

e. The trithorax group of proteins are activators of hox genes.

Q4 Signal transduction pathways in bacteria regulate cellular functions in response to environmental signals. Identify the correct statement

a. Both sensing and regulatory domains are present in one protein in two-component signal transduction systems (2CS).

b. Signal transduction occurs by His-Asp phosphotransfer in 2CS.

c. One component signal transduction systems (1CS) are well suited for detecting extracellular stimuli.

d. In response to a stimulus, the kinase component in the sensor protein of 2CS autophosphorylates at an internal aspartate (the H-box).

e. In both, 1CS and 2CS, a stimulus auto-phosphorylates at an internal histidine. The high-energy phosphate group is then transferred to an aspartate residue on the response regulator component which modifies cellular behaviour via an effector domain.