#Question id: 2898
#Unit 2. Cellular Organization
The human genome is composed of many different types of DNA sequences, the majority of which do not encode proteins. From the following distribution and amount of each of the various types of sequences determine which of these is CORRECTLY expressed?
#Question id: 2899
#Unit 2. Cellular Organization
The H3.H4 tetramers and H2A.H2B dimers each interact with a particular region of the DNA within the nucleosome.
I. Histone H3.H4 tetramers occupy a key position in the nucleosome by binding the middle and both ends of the DNA.
II. The amino-terminal region of H3 most proximal to the histone-fold region forms a fourth a-helix that interacts with the final 13 bp at each end of the bound DNA.
III. The relatively short length of DNA bound by H2A.H2B dimers is sufficient to prepare the DNA for H3.H4 tetramer binding.
IV. The H3.H4 tetramer forms the bottom part of the histone octamer located across the disc from the DNA ends whereas two H2A.H2B dimer occupies the top part.
Which of the following represents the correct binding of the histones with the DNA?
#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.