You will need to answer all the questions. Your homework will be graded automatically and recorded. Which of the following is NOT true about viruses. Some viruses, called retroviruses, have an RNA-based genome that requires creation of a DNA copy before the virus can replicate. Some viruses are surrounded by a membrane.
Viruses require a host cell in which to replicate.
All viruses that have an RNA genome contain reverse transcriptase to convert their RNA genome into a DNA copy. In Hfr conjugation of bacteria, two bacteria physically join and exchange DNA, so each gets DNA from the other. Extrachromosomal DNA must contain a bacterial origin of replication to be replicated in a bacterium. In the trp operon, tryptophan is the co-repressor of the system. The enzymes needed for making tryptophan are only made in significant amounts if tryptophan is present in the medium.