Which of the following statements about gene regulation concerning operons is incorrect? a) a negative repressible gene is controlled by a regulatory protein that inhibits transcription. b) for a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to dna. c) for a gene under positive repressible control, the normal state is transcription of a gene, stimulated by a transcriptional activator. d) a regulator gene has its own promoter and is transcribed into an independent mrna. e) presence of operons where genes of related functions are clustered is common in bacteria but not in eukaryotes.

Which type of neuron stimulates muscles to contract?

Match each law or principle to its description. 1. law of original horizontality sediment continues to spread in a flat plane until it hits an edge or runs out of material. 2. law of superposition the youngest strata are at the top and the oldest are at the bottom. 3. law of original lateral continuity sediment gets pulled down by gravity in a horizontal and flat layer. 4. law of cross-cutting or intrusive relationships if there is a fracture or intrusive feature seen in rock strata, it is younger than the rock strata.

Many birth-control pills release a constant amount of synthetic estradiols and progesterone for 21 days, followed by 7 days when no hormones are ingested. which of the following statements most accurately describes the effects of birth-control pills? -birth-control pills maintain constant levels of estrogens and/or progesterone so there is no surge in lh and ovulation does not occur.-birth-control pills inhibit the development of the uterine lining so implantation of a fertilized oocyte cannot occur.-birth-control pills maintain constant levels of estrogens and/or progesterones and mask the release of the oocyte from the follicle.-the 7 days with no hormones does not allow a thick enough uterine lining to form so a fertilized oocyte cannot implant.