Chapter 5 - The structure and Versatility of RNA Flashcards
The structure and versatility of RNA
How does RNA differ from DNA?
The backbone of RNA contains ribose rather than 2’-deoxyribose. That is, ribose has a hydroxyl group at the 2’ position. Second, RNA contains uracil in place of thymine. Uracil has the same single-ringed structure as thymine, except that it lacks the methyl group at position 5 (thymine = 5-methyl uracil). Thirdly, RNA is found as a single polynucleotide chain.
What are the functions of RNA?
Functions as an intermediate (mRNA) between the gene and the protein-synthesizing machinery. Functions as an adaptor, the RNA (tRNA) between the codon in the mRNA and amino acids. RNA can also play a structural role, as in the case of the RNA components of the ribosome. Another role for RNA is as a regulatory molecule, which though sequence complementarity binds to and interferes with the translation of, certain mRNAs. Finally, some RNAs are enzymes that catalyse essential reactions in the cell.
Name the types of folded structures RNA can take shape in.
- Stem-loop structure (intervening RNA is looped out from the end of the double-helical segment).
- Internal loops (unpaired nucleotides on either side of the stem)
- Bulges (an unpaired nucleotide on one side of the bulge)
- Junctions
What is a pseudoknot?
Base pairing that takes place between sequences that are not contiguous to form complex structures.
Give an example of an non-Watson-Crick base pairs.
G:U bas repair, which has hydrogen bonds between N3 uracil and the carbonyl on C6 of guanine, and between the carbonyl on C2 of uracil and N1 of guanine .
What prevents RNA from adapting B-helix form? And which form does RNA usually resemble?
The presence of 2’-hydroxyls in the RNA backbone prevents RNA from adopting a B-form helix. Usually the A-form structure of DNA –> less suitable for sequence-specific interactions with proteins.
Why doesn’t DNA show a self-cleavage mechanism?
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