#Question id: 2900
#Unit 2. Cellular Organization
Which of the following statement is INCORRECT from the set of statements given below?
#Question id: 2901
#Unit 2. Cellular Organization
HOTAIR is a lncRNA whose gene is found in the HoxC cluster in humans, but it acts by regulating expression of the HoxD genes on another chromosome (in trans) by recruiting to that locus Polycomb Repressive Complex 2 (PCR2). Which of the following processes is incorrect regarding this regulation?
#Question id: 2902
#Unit 2. Cellular Organization
The function and positioning of the histone variants can be studied by an application of technologies used in genomics. One useful technology is chromatin immunoprecipitation, or chromatin IP (ChIP). The correct sequence of the processes that occur in this experiment will be?
1. A histone variant with an epitope tag is introduced into a particular cell type, where it is incorporated into nucleosomes.
2. The pattern of hybridization on the microarray reveals the DNA sequences bound by the nucleosomes with the histone variant.
3. Antibody is added, and the nucleosomes containing the epitope-tagged histone variant are selectively precipitated.
4. Chromatin is isolated from the cells and digested briefly with micrococcal nuclease (MNase).
5. The DNA in these nucleosomes is extracted from the precipitate, labeled, and used to probe a microarray representing all or part of the genomic sequences of that particular cell type.
#Question id: 2903
#Unit 2. Cellular Organization
There are five known families of enzyme complexes that actively move or displace nucleosomes, hydrolyzing ATP in the process, three of which are particularly important in transcriptional activation. Which of the following statement is/are correct regarding these nucleosome remodeling complexes?
I. SWI/SNF remodels chromatin so that nucleosomes become more irregularly spaced, and stimulate the binding of transcription factors. It includes a bromodomain near the C-terminus of the active ATPase subunit, which interacts with acetylated histone tails.
II. Some members of a family, SWR1, are involved in deposition of the H2A.Z histone variant in transcriptionally inactive chromatin.
III. NURF, a member of the ISW1 family, remodels chromatin in ways that complement and overlap the activity of SWI/SNF. These two enzyme complexes are crucial in preparing a region of chromatin for active transcription.
#Question id: 2904
#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 properties gets changed due to subsequent denaturation of the DNA molecule?
#Question id: 2905
#Unit 2. Cellular Organization
With respect to X-chromosome inactivation, which, if any, of the following statements are not correct?
I. X-chromosome inactivation in mammals begins in the pre-implantation embryo
II. In humans all diploid cells that carry two normal X-chromosomes are subject to a random pattern of X-inactivation.
III. Once a decision has been made to inactivate an X chromosome (either the paternal or maternal X), all descendant cells show the same pattern of X-inactivation.
IV. The inactivated X chromosome becomes a highly condensed Barr body in which genes are silenced across the length of the chromosome.