Figure 2. Evolutionary layers of the X and Y chromosomes. (a) Comparative mapping of genes from the human X in marsupial mammals detected an ancient region conserved on the X in all mammals and denoted XCR, as well as a recently added region denoted XAR that is autosomal in marsupials.
Poliovirus, the causative agent of poliomyelitis (commonly known as polio), is a human enterovirus and member of the family of Picornaviridae. Poliovirus is composed of an RNA genome and a protein capsid. The genome is a single-stranded positive-sense RNA genome that is about 7500 nucleotides long.
The Creation and Production of the Polio Vaccines. In the 1950s, scientists like Doctors Jonas Salk and Albert Sabin had isolated the poliovirus strains to make vaccines.[1] Dr. Salkâs strains would be inactivated with formaldehyde and injected into children.