RNA is usually single stranded, so is more flexible than DNA.

RNA is created from DNA through the process of transcription.

Messenger RNA (mRNA)

From the central dogma we know RNA is translated into protein. Messenger RNA is translated into proteins.

Structure, particular in the 5' and 3' untranslated regions, contribute to post-transcription regulation such as splicing, translational efficiency and mRNA stability.

Non-coding RNA (ncRNA)

There are types of RNA that are not messenger RNA, and will not be translated into proteins, but still have function.

Transfer RNA (tRNA)

These RNA help with translation. They specify which codon (three-nucleotide sequence) corresponds to which amino acid.

They have an anticodon loop, and a 3' tail where the amino acid is attached.

Ribosomal RNA (rRNA)

The ribosome is approximately 60% rRNA and 40% protein by weight.

Used for translating mRNA into a polypeptide.

Small interfering RNA (siRNA)

Silences transcription.

long non-coding RNA (lncRNA)

The X-inactive specific transcript (Xist) gene encodes a large non-coding RNA that is responsible for mediating the specific silencing of the X chromosome from which it is transcribed.

Micro RNA (miRNA)

microRNAs down regulate mRNA by suppressing start of translation, promoting mRNA degrading, and transcription silencing.


The spliceosome contains five different RNA.

Signal recognition particle> is RNA and protein complex.


RNA forms structures with stems and loops.

Stems are formed between complementary pairs A-U and C-G, similar to DNA ladder.

Because of these stems, RNA sequence evolution allow sequence changes as long as base pairing in the stem region is retained. This allow the structure to remain intact. Sequence evolution is additionally constrained by structure.

Sequence similarity may be low for homologous RNA

The stems are nested in the linear sequence, and may be long distances apart.

When searching databases, it is beneficial to be able to take this into account.