Question

In plants, heterochromatinization of repeat sequences may be mediated by

• A. riboswitch-containing mRNAs.

• B. formation of nuclear pore-associated chromatin loops.

• C. histone hyperacetylation.

• D. RNA-directed DNA methylation.

When mRNAs lacking a poly(A) tail compete with polyadenylated mRNAs for
limiting translational machinery

• A. the polyadenylated mRNA is translated more efficiently.

• B. the efficiency of translation depends on the sequence of the mRNA, not the poly(A) tail.

• C. the mRNAs are translated equally efficiently.

• D. the mRNA lacking a poly(A) tail is translated more efficiently.

Answer 1

1. Option D is correct
In plants, heterochromatinization of repeat sequences may be mediated by RNA-directed DNA methylation.
DNA methylation at the cytosine residues is an epigenetic repression mark.

2. Option A is correct
The poly-A tail is located towards the 3'-end of the mature mRNA.
It increases the efficiency of translation.
It also provides stability to the mRNA.