You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium. Next you isolate a mutation, designated MelB–, which gives uninducible melibiase activity. Mapping experiments show that MelB– is linked to Mel1. Using an F' factor that carries the chromosomal region surrounding Mel1, you perform the following genetic tests:

 

Describe the proposal for the type of regulatory functions affected by the MelB– mutation.

TLS Online TPP Program

#Question id: 4469

#Unit 3. Fundamental Processes

Termination is a normal and important function at the ends of genes. There, sequences called terminators trigger the elongating polymerase to dissociate from the DNA and release the RNA chain it has made, In bacteria, terminators come in two types: Rho-dependent and Rho-independent, choose correct statements about this;

Rho-dependent	a- rut sites
	b- has an ATPase activity
Rho-independent	c- terminates only those transcripts still being transcribed beyond the end of a gene or operon
	d- intrinsic terminator

TLS Online TPP Program

#Question id: 386

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following properties of water does not contribute to the fitness of the aqueous environment for living organisms?

TLS Online TPP Program

#Question id: 15843

#Unit 8. Inheritance Biology

You have isolated two temperature-sensitive mutations in phage l that you suspect may be in the same gene. These phage mutants are called ts-1 and ts-2. Each mutant will form plaques at 35˚C but not at 42˚C. You cross ts-1 to ts-2 phage by coinfecting E. coli at the permissive temperature of 35˚C. When the resulting phage lysate is plated at 35˚C you count 10,000 plaques per ml of phage lysate, but when the same phage lysate is plated at 42˚C, there are only 80 plaques per ml.           What is the distance between the ts-1 and ts-2 mutations in m.u.?

TLS Online TPP Program

#Question id: 11692

#Unit 7. System Physiology – Animal

In the circulatory system of a fetus, which of the following is greater before birth than after birth ?

TLS Online TPP Program

#Question id: 12988

#Unit 10. Ecological Principles

Population ecologists follow the fate of same-age cohorts to