Following statements are regarding to PAR proteins and the establishment of polarity during early development in nematodes.

A. The internal cytoplasm contains PAR-3, PAR-6, and PKC-3, and the cortical cytoplasm contains PAR-2 and PAR-1.

B. PAR-3 and PAR-6, interacting with the protein kinase PKC-3 are uniformly distributed in the cortical cytoplasm. PKC-3 restricts PAR-1 and PAR-2 to the internal cytoplasm by phosphorylating them.

C. Once PAR-1 is in the cortical cytoplasm, it phosphorylates PAR-3, causing PAR-3 (and its binding partner, PKC-3) to leave the cortex.

D. During first cleavage, the metaphase plate is closer to the posterior, and the fertilized egg is divided into two cells, one having the anterior PARs (PAR-1 and PAR-2) and one having the posterior PARs (PAR-3 and PAR-6).

Which of the following statements are correct?

#Question id: 2882

#Unit 2. Cellular Organization

SUMO (small ubiquitin-related modifier) proteins are ∼10-kD polypeptides that function as reversible post-translational protein modifiers. They form isopeptide bonds with ɛ-amino groups of acceptor Lys residues in hundreds of target proteins in a process termed as sumoylation. Which of the following statements is correct regarding this modification?

#Question id: 2883

#Unit 2. Cellular Organization

Which, if any, of the following statements is incorrect?

I. In X-chromosome inactivation, the inactivated X chromosome is epigenetically silenced by a transcript, the XIST RNA, that is produced from the active X chromosome.

II. The XIST RNA works by coating most of the X chromosome that is to be inactivated and then recruiting Polycomb proteins to condense the chromosome.

III. The inactivated X chromosome carries the kinds of histone modification that are typical of heterochromatin.

IV. The pattern of X-chromosome inactivation is made randomly but once it has been established the same pattern of X-inactivation is propagated through all mitotic and meiotic cell divisions.

#Question id: 2884

#Unit 2. Cellular Organization

When the temperature of a solution of DNA is raised to near the boiling point of water, the optical density, (called absorbance) at 260 nm markedly increases, a phenomenon known as hyperchromicity. Which of the following statement is INCORRECT from the given set of statements?

#Question id: 2885

#Unit 2. Cellular Organization

Which of the following function of DNA methylation in mammalian cell is incorrect?

#Question id: 2886

#Unit 2. Cellular Organization

Match the following sites of modifications on histones given in Column I with their effect on transcription given in Column II.

#Question id: 2887

#Unit 2. Cellular Organization

Which of the following reasons has led to the evolutionary selection of an extra methyl group in DNA?