What is a component of RNA only?

Question

Adenine, cytosine, guanine, thymine or uracil?

Answer 1

Centromere RNA is a key component for the assembly of nucleoproteins at the nucleolus and centromere.

Centromeres are highly complex chromosomal substructures involved in essential aspects of chromosome transmission during cell division. The centromere/kinetochor complex is responsible for directing chromosome movements in mitosis and for faithful progression of mitotic events at the transition between metaphase and anaphase.

Accurate chromosome segregation relies on the interactions between the centromere/kinetochor complex and the spindle apparatus. Aberrant chromosome transmission causes genomic instability which can result in common birth defects, spontaneous abortions and is also tightly correlated with almost all types of cancer. In addition, viral proteins are able to target specific centromere components causing the destruction of the centromere complex and subsequent cell-cycle arrest of the host cell.

Within the cell nucleus centromeres undergo changes in their intranuclear localization during the cell cycle. They have been found to associate or colocalize with subnuclear structures, such as the nucleolus or nuclear bodies. Dynamic interactions between centromeres and other nuclear substructures may be important in controlling gene expression and centromere function as well.

Answer 2

The answer is Uracil.  It replaces Thymine in the DNA system.