A virus with RNA-dependent RNA polymerase A: synthesizes DNA from an RNA template. B: synthesizes double-stranded RNA from an RNA template. C: synthesizes double-stranded RNA from a DNA template. D: transcribes mRNA from DN

In positive regulation, most of the genes are usually inactive (that is, RNA polymerases do not bind to the promoters) and the cell synthesizes only the activator proteins needed to promote transcription of the subset of genes required in the cell at that time.

Which<br/>reactions is radical reaction() A: acetylene reacted with Cl2 B: Carbon<br/>tetrachloride is prepared from methane with light C: Isoprene<br/>synthesizes natural rubber D: Ethene<br/>reacted with HCl

Which<br/>reactions is radical reaction () A: Ethylene reacted with Cl2 B: Carbon<br/>tetrachloride is prepared from methane with light C: Isoprene<br/>synthesizes natural rubber D: Ethanol<br/>reacted with HCl

DNA polymerase probably synthesizes in the 5'→3'direction because A: that is the opposite direction of the replication fork B: that is the only way it can bind to DNA C: that allows synthesis to resume easily if one base needs to be removed D: this is the only direction permitted by the double helix

RNA polymerase: () A: binds tightly to a region of DNA thousands of base pairs away from<br/>the DNA to be transcribed. B: can synthesize RNA chains without a primer. C: has a subunit called λ (lambda), which acts as a proofreading<br/>ribonuclease. D: separates DNA strands throughout a long region of DNA (up to<br/>thousands of base pairs), then copies one of them. E: synthesizes RNA chains in the 3' →direction.