During  a  field  trip,  an  instructor  touched  a  moth  resting  on  a  tree  trunk.  The  moth  raised  its  forewings  to  reveal large eyespots on its hind wings. The instructor asked why the moth lifted its wings. One student answered that sensory  receptors  had  fired  and  triggered  a  neuronal  reflex  culminating  in  the  contraction  of  certain  muscles.  A second student responded that the behaviour might frighten predators. Which statement best describes these explanations?

#Question id: 2896

#Unit 2. Cellular Organization

Different modification states of the residue Lys-9 on the tail of histone H3 could be interpreted to have different meanings. One example of how a histone modification can apparently influence a second modification present nearby is illustrated by the Drosophila HP1 protein. Which of the following statement is correct regarding this kind of epigenetic regulation?

#Question id: 2897

#Unit 2. Cellular Organization

The transcription of most protein coding genes in mammals (~70 percent) occurs at a lower rate than at TATA box–containing and initiator-containing promoters and begins at any of several alternative start sites within regions of about 100–1000 bp that have an unusually high frequency of CG sequences. Which one of the following best explains it?

#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?