The Chemical Structure of ABA Determines Its Physiological Activity, 15 carbon compound 

a) The orientation of the carboxyl group at carbon 2 determines the cis and trans isomers of ABA. Nearly all the naturally occurring ABA is in the cis form

b) S enantiomer is the natural form; commercially available synthetic  ABA is a mixture of approximately equal amounts of the S and R forms.

c) The S enantiomer is the only one that is active in fast responses to ABA, such as stomatal closure

d) In long-term responses, such as seed maturation, only R-enantiomers are active

e) In contrast to the cis and trans isomers, the S and R forms cannot be interconverted in the plant tissue

Which of the following is the correct prediction about the active form  of ABA?

#Question id: 2878

#Unit 2. Cellular Organization

Match the following types of Transposable elements with their respective types and examples found in various organisms.

#Question id: 2879

#Unit 2. Cellular Organization

Hybridization between mature mRNA and DNA can identify introns in eukaryotic genes. When mature mRNA produced by the insulin gene is hybridized with denatured chromosomal DNA, which of the following will most likely be observed?

#Question id: 2880

#Unit 2. Cellular Organization

According to the manner in which they work, three main classes of proteins that modify chromatin are recognized. Match the following classes of proteins given in COLUMN I with their respective examples in COLUMN II.

#Question id: 2881

#Unit 2. Cellular Organization

Depletion of a 2.2-kb noncoding RNA expressed from the HOXC locus by siRNA unexpectedly led to derepression of the HOXD locus on another chromosome encoding several Hox proteins and multiple other noncoding RNAs, in these cells. Assays similar to chromatin immunoprecipitation showed that this noncoding RNA, named HOTAIR, associates with the HOXD loci and with PRC2 complexes. This association results in

i. Histone H3K9 di- and trimethylation

ii. H2B monoubiquitinylation

iii. Histone H3K4 demethylation

iv. H2A monoubiquitinylation

v. Histone H3K4 methylation

vi. Histone H3K27 di- and trimethylation

Which of the following results is CORRECT regarding this association?

#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.