Besides the sequences that are transcribed into RNA molecules, other kinds of information encoded in DNA include a. the beginning and end of genes. A DNA sequence that interrupts the coding region of a eukaryotic gene is called a. an exon. When RFLPs are used to distinguish genetic differences between DNA molecules of unknown origin, they serve as a. recessive traits. Viruses are the smallest living cells. The reverse transcriptase of HIV is a good target for antiviral drugs because human cells do NOT encode a reverse transcriptase.
Many animal viruses contain an exterior lipid membrane with inserted proteins.
Unlike most animal viruses, bacteriophages can NOT insert their genome into the host chromosome. A major problem with most cancer therapies is that they attack all dividing cells, including non-cancerous cells. Second messengers like IP3 are not proteins, but they may change the activities of proteins. Virtually all oncogenes are transcription factors, which bind DNA and regulate the expression of other genes. Because the disease retinoblastoma is inherited as a dominant trait, typically only one copy of the Rb is mutant in a cancerous cell.