Following statements were made regarding vulval development in C. elegans:

A. The formation of the anchor cell is mediated by lin-12, the C. elegans homologue of the Notch gene.

B. The formation of the anchor cell is mediated by lin-12, the C. elegans homologue of the Delta gene.

C. The lin-12 gene needs to function only in that cell destined to become the uterine precursor cell.

D. Presumptive Anchor cell also need lin-12.

E. Two cells originally synthesize both the signal for uterine differentiation (the LAG-2 protein, homologous to Delta) and the receptor for this molecule (the LIN-12 protein, homologous to Notch.

Which one of the following options represents a combination of correct statements?

TLS Online TPP Program

#Question id: 30103

#Unit 1. Molecules and their Interaction Relevant to Biology

Direct sources of purine ring atoms in the de novo synthesis of IMP include:

1. glutamine.

2. a component of the tetrahydrofolate one-carbon pool.

3. aspartate.

4. glycine.

TLS Online TPP Program

#Question id: 30104

#Unit 1. Molecules and their Interaction Relevant to Biology

A nucleoside phosphorylase:

1. cleaves a nucleoside with the production of ribose 1-phosphate.

2. is necessary for the major salvage pathway for pyrimidines.

3. is used in the degradation of purine nucleotides.

4. is responsible for the equilibration of nucleoside monophosphates and nucleoside diphosphate.

TLS Online TPP Program

#Question id: 30105

#Unit 1. Molecules and their Interaction Relevant to Biology

Methotrexate is an inhibitor of dihydrofolate reductase. Administration of methotrexate would inhibit:

1. de novo synthesis of UMP.

2. conversion of dUMP to dTMP.

3. conversion of IMP to GMP.

4. de novo synthesis of IMP

TLS Online TPP Program

#Question id: 30106

#Unit 1. Molecules and their Interaction Relevant to Biology

If a cell has an adequate supply of adenine nucleotides but requires more guanine nucleotides for protein synthesis:

1. Glutamine-PRPP amidotransferase will not be fully inhibited.

2. AMP will be a feedback inhibitor of the condensation of IMP with aspartate.

3. ATP will stimulate the production of GMP from IMP.

4. ATP will inhibit nucleoside diphosphate reductase.

TLS Online TPP Program

#Question id: 30107

#Unit 1. Molecules and their Interaction Relevant to Biology

Major controls of de novo AMP synthesis include:

1. allosteric inhibition by GMP.

2. allosteric inhibition by AMP.

3. availability of PRPP.

4. stimulation by GTP.

TLS Online TPP Program

#Question id: 30108

#Unit 1. Molecules and their Interaction Relevant to Biology

Aspartate plays a role in all of the following EXCEPT: