Exons of a gene are defined as
(a) the untranslated regions of the corresponding mrna
(b) regions in the corresponding mrna that are involved in initiation of transcription
(c) regions that are not transcribed by rna polymerase
(d) regions that are excised from the corresponding protein after it is synthesized
(e) regions that remain in the corresponding mrna after splicing

Which of the following occurs most often in a population when genetic variation and overproduction are present? some organisms have a lower reproductive success than others. some organisms have a higher reproductive success than others. some organisms have no reproductive success. some organisms do not have genetic variation.

Keeping in mind the life cycle of bacteriophages, consider the following problem: during the reproductive cycle of a temperate bacteriophage, the viral dna inserts into the bacterial chromosome where the resultant prophage behaves much like a trojan horse. it can remain quiescent, or it can become lytic and initiate a burst of progeny viruses. several operons maintain the prophage state by interacting with a repressor that keeps the lytic cycle in check. insults (ultraviolet light, for example) to the bacterial cell lead to a partial breakdown of the repressor, which in turn causes the production of enzymes involved in the lytic cycle. as stated in this simple form, would you consider this system of regulation to be operating under positive or negative control?

Which statement best describes how the nucleus, the rough endoplasmic reticulum, and ribosomes interact during protein synthesis?