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Orthopoxvirus particles. A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase.They can be divided between those that have two strands of DNA in their genome, called double-stranded DNA (dsDNA) viruses, and those that have one strand of DNA in their genome, called single-stranded DNA (ssDNA) viruses. dsDNA viruses primarily belong ...
The phi X 174 (or ΦX174) bacteriophage is a single-stranded DNA virus that infects Escherichia coli. This virus was isolated in 1935 by Nicolas Bulgakov [ 1 ] in Félix d'Hérelle 's laboratory at the Pasteur Institute , from samples collected in Paris sewers.
CRESS-DNA viruses therefore represent a notable instance of convergent evolution, whereby organisms that are not directly related evolve the same or similar traits. [1] The atypical members of Monodnaviria have various origins: Parvoviruses, which are linear ssDNA viruses, are likely to have evolved from CRESS-DNA viruses.
If a DNA segment under twist strain is closed into a circle by joining its two ends, and then allowed to move freely, it takes on different shape, such as a figure-eight. This shape is referred to as a supercoil. (The noun form "supercoil" is often used when describing DNA topology.) The DNA of most organisms is usually negatively supercoiled.
With DNA in its "relaxed" state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound. [43] If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together.
The diagram shows the effects of nicks on intersecting DNA in a twisted plasmid. Nicking can be used to dissipate the energy held up by intersecting states. The nicks allow the DNA to take on a circular shape. [2] The diagram shows the effects of nicks on intersecting DNA forms. A plasmid is tightly wound into a negative supercoil (a).
In DNA double helix, the two strands of DNA are held together by hydrogen bonds. The nucleotides on one strand base pairs with the nucleotide on the other strand. The secondary structure is responsible for the shape that the nucleic acid assumes. The bases in the DNA are classified as purines and pyrimidines. The purines are adenine and guanine ...
Bacillus virus Φ29 (bacteriophage Φ29) is a double-stranded DNA (dsDNA) bacteriophage with a prolate icosahedral head and a short tail that belongs to the genus Salasvirus, order Caudovirales, and family Salasmaviridae. [2] [3] They are in the same order as phages PZA, Φ15, BS32, B103, M2Y (M2), Nf, and GA-1.