Given a scientific passage and an answer, generate a question for the given answer.

Ex Input:
Passage: Restriction enzymes or restriction endonucleases are prokaryotic enzymes that recognize and cut DNA at specific sequences, called restriction sites. It is believed that they evolved as a defense mechanism against foreign DNA, such as viral DNA. Over 3,000 restriction enzymes have been identified. Some of the more common restriction enzymes are shown in the table below, where up and down arrows show the sites of cleavage. Restriction enzymes are named based on the prokaryotic organism they are isolated from. For example, those isolated from Escherichia coli would begin with Eco. As the Table below shows, digestion with the restriction enzymes will result in overlapping or blunt ends. EcoRI produces overlapping "sticky" ends: the enzyme cleaves between the G and A on both strands. On the other hand, SmaII restriction enzyme cleavage produces "blunt" ends. The enzyme cleaves between the G and C on both strands. Answer: dna

Ex Output:
Restriction enzymes or restriction endonucleases are prokaryotic enzymes that recognize and cut what at specific sequences?


Ex Input:
Passage: Structure of the trp operon. The trp operon is composed of 5 structural genes, 1 regulatory gene and other regulatory sequences, including the promoter, operator and leader sequence. Within the leader sequence is the attenuator region. In the presence of tryptophan, the structural genes are not transcribed. Answer: they are not transcribed

Ex Output:
What happens to structural genes in the presence of tryptophan?


Ex Input:
Passage: 37.2 How Hormones Work Hormones cause cellular changes by binding to receptors on target cells. The number of receptors on a target cell can increase or decrease in response to hormone activity. Hormones can affect cells directly through intracellular hormone receptors or indirectly through plasma membrane hormone receptors. Lipid-derived (soluble) hormones can enter the cell by diffusing across the plasma membrane and binding to DNA to regulate gene transcription and to change the cell’s activities by inducing production of proteins that affect, in general, the long-term structure and function of the cell. Lipid insoluble hormones bind to receptors on the plasma membrane surface and trigger a signaling pathway to change the cell’s activities by inducing production of various cell products that affect the cell in the short-term. The hormone is called a first messenger and the cellular component is called a second messenger. G-proteins activate the second messenger (cyclic AMP), triggering the cellular response. Response to hormone binding is amplified as the signaling pathway progresses. Cellular responses to hormones include the production of proteins and enzymes and altered membrane permeability. Answer: target cells

Ex Output:

Hormones cause cellular changes by binding to receptors on these?


