The adenovirus genome is linear, non-segmented double-stranded ( ds ) DNA that is between 26 and 45 Kbp.

Intracellular recognition of viral double-stranded ( ds ) and single stranded RNA has been shown to be mediated by a group of RNA Helicases which in turn recruit factors via twin N-terminal CARD domains to activate antiviral gene programs.

* Nucleic acid thermodynamics, includes the annealing of DNA or RNA pairing by hydrogen bonds to a complementary sequence, forming a double-stranded polynucleotide

The virus particle consists of 10 strands of double-stranded RNA surrounded by two protein shells.

# A poly-T oligonucleotide primer is hybridized onto the poly-A tail of the mature mRNA template, or random hexamer primers can be added which contain every possible 6 base single strand of DNA and can therefore hybridize anywhere on the RNA ( Reverse transcriptase requires this double-stranded segment as a primer to start its operation.

Short pieces of double-stranded RNA ( short, interfering RNAs or siRNAs ) are used by cells to degrade RNA of a particular sequence.

Toll Like Receptor 3 ( TLR3 ) is important for inducing interferon in response to the presence of double-stranded RNA viruses ; the ligand for this receptor is double-stranded RNA ( dsRNA ).

It is thought to be part of the innate immune system as a defense against double-stranded RNA viruses.

In most cases, naturally occurring DNA molecules are double-stranded and RNA molecules are single-stranded.

There are numerous exceptions, however — some viruses have genomes made of double-stranded RNA and other viruses have single-stranded DNA genomes, and, in some circumstances, nucleic acid structures with three or four strands can form.

However, the HIV-encoded reverse transcriptase has own ribonuclease activity that degrades the viral RNA during the synthesis of cDNA, as well as DNA-dependent DNA polymerase activity that copies the sense cDNA strand into an antisense DNA to form a double-stranded DNA intermediate.

* Unlike double-stranded DNA, RNA is a single-stranded molecule in many of its biological roles and has a much shorter chain of nucleotides.

One way antisense RNA can act is by binding to an mRNA, forming double-stranded RNA that is enzymatically degraded.

dsRNA forms the genetic material of some viruses ( double-stranded RNA viruses ).

This nucleic acid is usually single-stranded RNA ( ssRNA ), but may be double-stranded RNA ( dsRNA ).

One of these includes RNA-dependent RNA polymerase ( RNA replicase ), which copies the viral RNA to form a double-stranded replicative form, in turn this directs the formation of new virions.

In virus species with reverse transcriptase lacking DNA-dependent DNA polymerase activity, creation of double-stranded DNA can possibly be done by host-encoded DNA polymerase δ, mistaking the viral DNA-RNA for a primer and synthesizing a double-stranded DNA by similar mechanism as in primer removal, where the newly synthesized DNA displaces the original RNA template.

* DNA viruses ( divided into double-stranded DNA viruses and single-stranded DNA viruses ),

* RNA viruses ( divided into positive-sense single-stranded RNA viruses, negative-sense single-stranded RNA viruses and the much less common double-stranded RNA viruses ),

* reverse transcribing viruses ( double-stranded reverse-transcribing DNA viruses and single-stranded reverse-transcribing RNA viruses including retroviruses ).

An elaborate machinery of interacting enzymes detects double-stranded RNA molecules ( which occur as part of the life cycle of many viruses ) and then proceeds to destroy all single-stranded versions of those detected RNA molecules.

Baculoviruses are parasite double-stranded DNA insect viruses that are used mostly as biological control agents.

Baltimore classification ( first defined in 1971 ) is a classification system that places viruses into one of seven groups depending on a combination of their nucleic acid ( DNA or RNA ), strandedness ( single-stranded or double-stranded ), Sense, and method of replication.

* Group I: viruses possess double-stranded DNA.

Adenoviruses are medium-sized ( 90 – 100 nm ), nonenveloped ( without an outer lipid bilayer ) icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome.

Well-conserved features in pathogens include bacterial cell-surface lipopolysaccharides ( LPS ), lipoproteins, lipopeptides, and lipoarabinomannan ; proteins such as flagellin from bacterial flagella ; double-stranded RNA of viruses ; or the unmethylated CpG islands of bacterial and viral DNA ; and certain other RNA and DNA.

Small DNA tumor viruses are a group of double-stranded DNA viruses, made up of the polyomavirus, the adenovirus and the papillomavirus families.

This small group of viruses, exemplified by the Hepatitis B virus, have a double-stranded, gapped genome that is subsequently filled in to form a covalently closed circle ( ccc DNA ) that serves as a template for production of viral mRNAs and a subgenomic RNA.

This is probably because the papillomavirus genome is composed of genetically stable double-stranded DNA that is replicated with high fidelity by the host cell's DNA replication machinery.

This sort of mechanism is thought to be important in cellular defense against RNA viruses and / or transposons, both of which often form a double-stranded RNA that can be mutagenic to the host genome.

Like most viruses with RNA genomes, double-stranded RNA viruses do not rely on host polymerases for replication to the extent that viruses with DNA genomes do.

The desired gene together with a promoter to drive transcription of the gene is inserted between the inverted terminal repeats ( ITR ) that aid in concatamer formation in the nucleus after the single-stranded vector DNA is converted by host cell DNA polymerase complexes into double-stranded DNA.

This process in a eukaryotic nucleus can give rise to concatemeric double-stranded forms of replicative intermediate genomes, although double-stranded unit circles can be isolated from infected plants and cells.

For example, naked double-stranded DNA ends would usually be interpreted by the cell as damaged or viral DNA, triggering cell cycle arrest, DNA repair, or destruction of the DNA fragment such as by endonucleases in bacteria.

Alternatively, worms can be fed genetically transformed bacteria which express the double-stranded RNA of interest.

Siphoviridae are a family of double-stranded DNA viruses infecting only bacteria.

Other PAMPs include bacterial flagellin ( recognized by TLR 5 ), lipoteichoic acid from Gram positive bacteria, peptidoglycan, and nucleic acid variants normally associated with viruses, such as double-stranded RNA ( dsRNA ), recognized by TLR 3 or unmethylated CpG motifs, recognized by TLR 9.

The inverted repeat palindrome is also a sequence that reads the same forward and backwards, but the forward and backward sequences are found in complementary DNA strands ( i. e., of double-stranded DNA ), as in GTATAC ( GTATAC being complementary to CATATG ).

Small interfering RNA ( siRNA ), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA molecules, 20-25 nucleotides in length.

Polyomaviruses are DNA-based ( double-stranded DNA, ~ 5000 base pairs, circular genome ), small ( 40-50 nanometers in diameter ), and icosahedral in shape, and do not have a lipoprotein envelope.

This process involves the separation of the double-stranded DNA in high heat into single strands ( the denaturation step, typically achieved at 95 – 97 ° C ), annealing of the primers to the single stranded DNA ( the annealing step ) and copying the single strands to create new double-stranded DNA ( the extension step that requires the DNA polymerase ) requires the reaction to be done in a thermal cycler.

Restriction endonucleases may be found that cleave standard dsDNA ( double-stranded DNA ), or ssDNA ( single-stranded DNA ), or even RNA.

Historically, the effects of antisense RNA have often been confused with the effects of RNA interference ( RNAi ), a related process in which double-stranded RNA fragments called small interfering RNAs trigger catalytically mediated gene silencing, most typically by targeting the RNA-induced silencing complex ( RISC ) to bind to and degrade the mRNA.