The subdivisions of the circulatory system are the , which carries blood to and from the lungs, and the , which carries blood to and from all other parts of the body. A. venous circuit, arterial circuit
B. arterial circuit, venous circuit
C. systemic circuit, pulmonary circuit
D. pulmonary circuit, systemic circuit

Poliovirus is an rna virus of the picornavirus group, which uses its rna as mrna. at its 5' end, the rna genome has a viral protein (vpg) instead of a cap. this is followed by anontranslated leader sequence, and then a single long protein-coding region (~7000 nucleotides), followed by a poly-a tail. observations were made that used radioactive amino acid analogues. short period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides. what conclusion is most consistent with the results of the radioactive labeling experiment? a) host cell ribosomes only translate the viral code into short polypeptides. b) the rna is only translated into a single long polypeptide, which is then cleaved into shorter ones. c) the rna is translated into short polypeptides, which are subsequently assembled into large ones. d) the large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.

Viruses use the host's machinery to make copies of themselves. however, some human viruses require a type of replication that humans do not normally have. for example, humans normally do not have the ability to convert rna into dna. how can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires? a) the virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles. b) the viral genome codes for specialized enzymes not in the host. c) the virus infects only those cells and species that can perform all the replication roles necessary. d) viruses can stay in a quiescent state until the host cell evolves this ability.

Why do males take longerto heal from a broken heart?