How does dna differ from rna

Before we delve into the differences, we take a look at these two nucleic acids side-by-side. I Understand. Published: December 18, Last Updated: November 11, DNA encodes all genetic information, and is the blueprint from which all biological life is created.

In the long-term, DNA is a storage device, a biological flash drive that allows the blueprint of life to be passed between generations 2. RNA functions as the reader that decodes this flash drive.

This reading process is multi-step and there are specialized RNAs for each of these steps. Below, we look in more detail at the three most important types of RNA. The nitrogen bases in DNA are the basic units of genetic code, and their correct ordering and pairing is essential to biological function. The four bases that make up this code are adenine A , thymine T , guanine G and cytosine C.

Epigenetic Modifications 2. Untranslated regions: Untranslated regions UTRs are nucleotide stretches that flank the coding region and are not translated into amino acids. These regions are part of the primary transcript and remain after the splicing of exons into the mRNA. As such UTRs are exonic regions. Several functional roles have been attributed to the untranslated regions, including mRNA stability, mRNA localization, and translational efficiency. Coding regions begin with the start codon and end with a stop codon.

This tail promotes export from the nucleus, translation, and stability of mRNA 13 , The structure of an mRNA 3. RNA interference in mammalian cells Designer siRNAs are now widely used in the laboratory to down-regulate specific proteins whose function is under study. Non protein coding RNAs a. More than one thousand miRNAs are currently known for the human genome, and each of them has the ability to down regulate the expression of possibly thousands of protein coding genes Alternative pathways non-canonical Drosha independent pathways: As mentioned above, most miRNAs either originate form their own transcription units or derive from the exons or introns of other genes 33 and require both Drosha and Dicer for cleavage in their maturation.

It was recently shown however first in Droshophila 33 and later in mammals 34 that short hairpin introns, called mirtrons can be alternative sources of miRNAs. Although there are several differences between mammalian and invertebrate mirtrons, both are Drosha independent.

Mirtrons are short introns with hairpin potential that can be spliced and debranched into pre-miRNA mimics and then enter the canonical pathway. Importantly, the Ago catalytic function for the miR biogenesis was shown in Ago2 homozygous mutants that were found to have loss of miR and died shortly after their birth with anemia Not all nucleotides of the seed region need to be paired for the heteroduplex to have a functional effect 18 , 35 — The base-pairing in the seed region can comprise Watson-Crick bonding, although this was recently shown to neither be necessary 31 nor sufficient However, it was recently shown that animal miRNAs could target mRNA coding regions equally effectively and extensively In plants, miRNA targeting is predominantly through coding region targets.

The possible mechanisms include: translational inhibition 38 ; removal of the poly A tail from mRNAs deadenylation 39 , 40 ; disruption of cap—tail interactions 41 , 42 ; and, mRNA degradation by exonucleases 43 , 44 , although highly complementary targets can be cleaved endonucleolytically Other types of regulatory function of miRNAs have also been described, and include translational activation 46 , heterochromatin formation 47 , and DNA methylation The standard naming system uses abbreviated three letter prefixes to designate the species e.

The number is assigned by the miRBase Registry. Orthologous miRNAs across organisms differ only in their species name e. Nearly identical miRNAs that differ at only one or two positions are distinguished by lettered suffixes e. Paralogous miRNAs, i. They are intermediate-sized RNAs of nucleotides in length and are predominantly found in the nucleus Two major classes of snoRNAs have been identified which possess distinctive, evolutionary conserved sequence elements. These modifications are important for the production of efficient ribosomes These RNA-protein complexes are involved in the epigenetic and and post-transcriptional gene silencing of transposable and other repetitive elements 58 , They have been found in the tunicate Ciona intestinalis but also in human microRNA precursors, albeit in low levels 27 , The high level of conservation and the example of miR with moRNAs conserved between humans and Ciona suggests that they might have a functional role 27 , A large number of such RNAs have been identified and constitute the largest portion of the mammalian non-coding transcriptome.

Such RNAs have been identified in both protein-coding loci and also within intergenic stretches. Attempts to functionalize these other classes of ncRNAs are currently in their very early stages. LincRNAs arise from intergenic regions and exhibit a specific chromatin signature that consists of a short stretch of trimethylation of histone protein H3 at the lysine in position 4 H3K4me3 — characteristic of promoter regions, followed by a longer stretch of trimethylation of histone H3 at the lysine in position 36 H3K36me3 — characteristic of transcribed regions.

Transcripts from active enhancer regions with another chromatin signature, the H3 lysine 4 monomethylation H3K4me1 modification have also been described, although it is not clear whether they represent a distinct class of lincRNAs. This consists of five types of small nuclear RNA molecules snRNA and more than 50 proteins small nuclear riboprotein particles. Proteins A protein is a molecule that performs reactions necessary to sustain the life of an organism.

Protein translation 5. References Bentley D. The mRNA assembly line: transcription and processing machines in the same factory. Current opinion in cell biology. Transcription of eukaryotic protein-coding genes. Annual review of genetics. Epigenetics in cancer. The New England journal of medicine. Chromatin modifications and their function. Non-coding RNA. Hum Mol Genet. Global identification of human transcribed sequences with genome tiling arrays.

Transcriptional maps of 10 human chromosomes at 5-nucleotide resolution. The transcriptional landscape of the mammalian genome. This information is taken from the DNA by the RNA, which is responsible for creating the blue pigment proteins necessary to express these genes. What Is a Homologous Allele? What Combination of Chromosomes Results in a Boy? Nucleic Acid Facts.

What Is the Diploid Number? Facebook Facebook Twitter Twitter. Updated February 02, Used to transfer the genetic code from the nucleus to the ribosomes to make proteins. RNA is used to transmit genetic information in some organisms and may have been the molecule used to store genetic blueprints in primitive organisms.

Structural Features B-form double helix. DNA is a double-stranded molecule consisting of a long chain of nucleotides. A-form helix. RNA usually is a single-strand helix consisting of shorter chains of nucleotides. Composition of Bases and Sugars deoxyribose sugar phosphate backbone adenine, guanine, cytosine, thymine bases ribose sugar phosphate backbone adenine, guanine, cytosine, uracil bases Propagation DNA is self-replicating.

The small grooves in the helix also serve as protection, providing minimal space for enzymes to attach. RNA is not stable under alkaline conditions, plus the large grooves in the molecule make it susceptible to enzyme attack.

RNA is constantly produced, used, degraded, and recycled. Featured Video. View Article Sources. Cite this Article Format.