A company claims its Bt cotton lowers total insecticide use. A 10-year survey finds sprays against bollworm fell sharply while sprays against sap-sucking mirid bugs rose, leaving liters per hectare unchanged. How does this bear on the claim?

Bacteria carrying the human insulin gene on a plasmid make insulin in a fermenter. A company claims the product is the same protein as human insulin. Analysis finds it has the same amino acid sequence as human insulin. How should this be judged?

A seed firm claims that growing its herbicide-tolerant soybeans will not produce weeds able to survive the herbicide. After 15 seasons of use, several weed species in those fields survive the herbicide at the recommended rate. What does this show?

A firm claims its therapy corrects the sickle cell mutation in patients' blood stem cells. Treated patients make far more fetal hemoglobin and have fewer pain crises, but the sickle allele is still present in their cells. How does this bear on the claim?

A DNA profile from a crime scene matches a suspect at every tested STR locus. The suspect has an identical twin brother living in the same town. How does the match bear on the claim that the profile came from this suspect rather than from his twin?

The hepatitis B vaccine is made by putting one viral surface-protein gene into yeast. Testing finds the product contains that protein and no viral genetic material. How does this bear on the claim that the vaccine cannot cause hepatitis B?

A city is deciding whether to keep releasing male mosquitoes engineered so that their offspring die before adulthood, in order to cut dengue. Which finding would count most strongly in favor of continuing the releases?

Farmers argue that herbicide-tolerant soybeans protect soil, because weeds can be killed by spraying instead of by plowing. Which evidence bears most directly on that argument?

A patient group argues that a gene therapy delivered by a virus should be approved for use in children. Which finding would count most strongly against approval?

A regulator is deciding whether to approve a herbicide-tolerant lawn grass for sale. Which finding would count most strongly against approval?

After a building collapse, a team argues that DNA profiling should be used to identify remains that cannot be recognized by sight. Which evidence supports that position most strongly?

Human growth hormone for children who cannot make enough was once extracted from pituitary glands taken from human cadavers. It is now made by bacteria carrying the human gene. What is the main benefit of the change for patients?

Before starting a family, two adults have their DNA read for recessive alleles that cause disease only when a child inherits two copies. What can the result usefully tell them?

A dairy company plans to build its whole herd from clones of one high-yielding cow, made by transferring nuclei from her body cells into egg cells. What is the likely risk of a herd built this way?

After a fuel spill, a team adds bacteria that break hydrocarbons down for energy to the contaminated soil. What is the likely benefit of this treatment?

A clinic uses PCR to detect a virus, copying any matching target sequence in a swab millions of times. What risk does that amplification create for the result?

A drought-tolerant transgenic maize out-yielded the unmodified variety at one test site in one growing season. A ministry must decide whether to recommend it to farmers across the country. Which additional information is most necessary?

A soybean is engineered with a gene from the Brazil nut so that the beans hold more of the amino acid methionine. Before the beans are sold as food, which additional data is most necessary?

Researchers propose releasing mosquitoes that carry a gene drive spreading a female-sterility allele through the mosquito population of one island. Which additional data is most necessary before the release?

A company proposes coating cereal seed with engineered bacteria that fix nitrogen on the crop's roots so that farmers can apply less fertilizer. Which additional information does a decision to approve the product most need?