#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.
COLUMN I COLUMN II
1) Methylation of H3K36 in transcribed region a) Activation
2) Ubiquitinylation of H2BK120 in mammals b) Repression
3) Phosphorylation of H2AT120 c) Elongation
4) Hypoacetylated Lysine
5) Acetylation of H4K8
#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?