You have isolated two mutations in the Lac operon that cause constitutive expression of Lac genes. You designate these mutants Lac1– and Lac2–. Making use of an F' that carries the Lac operon with the LacY gene mutated, you construct strains that you test for both ß-galactosidase activity and Lac permease activity with results shown below.

     

Classify each mutation as dominant or recessive and as cis- or trans-acting, giving the experimental result that allows you to arrive at each conclusion. Finally, deduce what type of Lac mutation best fits the properties of Lac 1– and of Lac 2–.

TLS Online TPP Program

#Question id: 1303

#Unit 4. Cell Communication and Cell Signaling

What is a primary function of integrins?

TLS Online TPP Program

#Question id: 3642

#Unit 3. Fundamental Processes

Any piece of DNA which replicates as a single unit is called

TLS Online TPP Program

#Question id: 73

#Unit 1. Molecules and their Interaction Relevant to Biology

Match the Variation of Reaction Spontaneity (Sign of ΔG) given in Column I with the Signs of ΔH and ΔS given in column II.

COLUMN I	COLUMN II
	ΔH	ΔS	ΔG = ΔH – TΔS
1.	−	+	a. The reaction is both enthalpically and entropically opposed. It is nonspontaneous (endergonic) at all temperatures.
2.	−	−	b. The reaction is enthalpically opposed (endothermic) but entropically favored. It is spontaneous only at temperatures above T = ΔH/ΔS.
3.	+	+	c. The reaction is enthalpically favored but entropically opposed. It is spontaneous only at temperatures below T = ΔH/ΔS.
4.	+	−	d. The reaction is both enthalpically favored (exothermic) and entropically favored. It is spontaneous (exergonic) at all temperatures.

TLS Online TPP Program

#Question id: 7143

#Unit 5. Developmental Biology

The development of drugs to block the activity of vascular endothelial growth factor (VEGF) has been applied to the control of the growth of cancers. What is the rationale for such a strategy?

TLS Online TPP Program

#Question id: 29510

#Unit 6. System Physiology – Plant

Which one of the following secondary metabolites is produced by  Members of the Brassicales and characterised by a sulphur-containing organic compounds derived from glucose and an amino acid?