Bacteria (easy)

Question 1

Explain the regulation of Arg operon [3]

Answer 1

1. Repressible operon
   » repressor synthesised is inactive (cannot bind to operator)
2. In presence of Arg&raquo_space; Arg binds repressor&raquo_space; changes its conformation&raquo_space; activated (can bind to operator)
3. Prevent RNA pol from binding to promoter&raquo_space; prevent Tsc

Question 2

State function of beta-galactosidase [1]

Answer 2

HYDROLYSE GLYCOSIDIC BOND

Question 3

Describe the positive regulation of the lac operon [3]

Answer 3

1. Low glucose&raquo_space; high cAMP&raquo_space; binds allosteric site of CataboLITE AP&raquo_space; activating CAP
2. Active CAP binds to CAP binding site at promoter
   » increase affinity of the promoter for RNA pol
3. In presence of lactose
   » this upregulates the expression of structural genes

Question 4

Explain 5 advantages of phage therapy > antibiotics

Answer 4

1. Specificity
2. Replicate at the site of infection where they are most needed
3. Non-toxic
4. Small quantity needed
5. Co-evolve vs. bacteriostatic antibiotics

Question 5

Define the term operon in context [2]

Answer 5

1. Group of genes X, Y and Z under the control of the same PROMOTER and OPERATOR
2. Allows for functionally related proteins to be synthesised as a unit
   » {state function - eg. metabolise lactose}

Question 6

Suggest why Tsc of structural genes proceeds in a different direction from the regulatory gene
[2]

Answer 6

1. Located on different strands
2. DNA is ANTI-PARALLEL
3. DNA template is read by DNA POL in 3’ to 5’ direction