71.

The amount of each enzyme present in the chloroplast stroma is regulated by mechanisms that control the concerted expression of nuclear and chloroplast genomes. Following are certain statements regarding the regulation of chloroplast enzymes:

A. Nucleus-encoded enzymes are translated on 70S ribosomes in the cytosol and subsequently transported into the plastid.

B. Plastid encodes enzymes are translocated in the stroma on prokaryote-like 70S ribosomes.

C. Light modulates the expression of stromal enzymes encoded by the nuclear genome via specific photoreceptors.

D. The eight small subunits of rubsico is encoded in plastid?

Which one of the following combinations of above statements is correct?

• A and B

• A and C

• B and C

• C and D

The following statements were made regarding chromosome pairing (shown in the figure below) and subsequent segregation during meiosis - I in the reciprocal translocation heterozygote:

A. Three ways of segregation in Anaphase I would be : adjacent 1 (vertically in the above figure), adjacent 2 (horizontally and alternate.

B. Gametes resulting from adjacent 1 and adjacent 2 segregation will be non-viable because of deletions and duplications of several genes.

C. All gametes resulting from alternate segregation will be viable as they will carry both normal chromosomes or both chromosomes having translocations in the two plea, respectively.

D. A dicentric and acentric chromosome will be generated following alternate segregation.

Which of the following combination of statements will most appropriately explain the consequence?

• A, B and D

• A, B and C

• Only A and B

• Only A and C

If a proteasome inhibitor is added to synchronously cycling human cells in G2 phase which one of the following events is likely to happen?

• Induce re-replication of DNA.

• Arrest cells in G2 phase

• Arrest cells in Anaphase

• Block chromatin condensation

In order to prove that liposome can serve as a model membrane (mimicking cellular plasma membrane) and can be used as a target for complement-mediated immunolysis, an experiment as below is designed. To initiate such experiment, hapten-conjugated liposomes are made and loaded with umbelliferyl phosphate (UMP; hydrolyzed product of UMP is umbelliferone and is fluorescent). Such loaded, hapten-conjugated liposomes in 10mM Tris-buffered saline, pH 7.4 were mixed with anti-hapten antibodies and fresh guinea pig serum (as a source of complement) to induce immunolysis of liposomal membrane. To quantify only the membrane lysis component which of the assay sequences below is MOST appropriate?

• Mixture is ultracentrifuged and the supernatant reacted with alkaline phosphatase and fluorescence measured.

• Mixture is sequentially reacted with phospholipase and alkaline phosphatase followed by fluorescence measurements.

• Mixture is directly subjected to fluorescence measurement.

• Mixture is treated with Triton X-100 and fluorescence measured.

Which of the following statements about meiosis is NOT true?

• Kinetochores of sister chromatids attach to opposite poles in Meiosis I.

• Kinetochores of sister chromatids attach to opposite poles in Meiosis II.

• Chiasma is formed in Prophase I.

• Homologous chromosomes are segregated in Meiosis I.

In chloroplast, the site of couples oxidation-reduction reactions is the

• outer membrane

• inner membrane

• thylakoid space

• stromal space

What will happen if histones are depleted from a metaphase chromosome and viewed under a transmission electron microscope?

• 30nm chromatin fibres will be observed.

• 10nm chromatin fibres will be observed.

• A scaffold and a huge number of loops of DNA fibres will be observed.

• A huge number of loops of DNA fibres without scaffold will be observed.

Which of the following statements regarding membrane transport is FALSE?

• Polar and charged solutes will not cross cell membranes effectively without specific protein carriers.

• Each protein carrier will only bind and transport one (or a few very similar) type of solute.

• Sugars such as glucose are always transported by active transport rather than by facilitated diffusion carriers.

• Ions are typically transported by special proteins that form membrane channels.

Proton motive force during oxidative phosphorylation is generated in mitochondria by

• exchanging protons for sodium ions 

• pumping protons out into intermembrane space.

• pumping hydroxyl ions into the mitochondria

• hydrolysis of ATP

The key determinant of the plane of cytokinesis in mammalian cells is the position of

• chromosomes

• central spindle

• centrioles

• pre-prophase band