bi Benchmark 2 (midpoint)

Enter your Student ID and answer each item. This is a check against the WebXam blueprint, not a grade. You will see some of these questions again at the next checkpoint.

1. 1. Incidence counts new cases in a period; prevalence counts:

   AThe size of the population at riskBExisting cases at one point in timeCNew cases that appear each weekDDeaths caused by the disease

2. 2. "Morbidity" refers to illness; "mortality" refers to:

   ADeaths in a populationBBirths in a populationCPatients who recoverDNew cases of the illness

3. 3. Contact tracing slows an outbreak by:

   ARunning ads that list the symptomsBFinding and notifying exposed peopleCVaccinating the whole community at onceDRecording the total population size

4. 4. Dose-response means the harmful effect depends mostly on:

   AWhether the substance is toxic, not how muchBHow strong the substance smellsCWhether the substance is natural or man-madeDHow much of the substance enters the body

5. 5. To judge a community's risk from a pollutant, you most need to know:

   AWhether a lab test detects itBHow many residents have complainedCConcentration and exposure over timeDHow the water looks and smells

6. 6. Most sick people ate at the same place first. This suggests:

   AA common source of exposureBThat the place is simply popularCAn inherited condition they shareDA seasonal illness going around

7. 7. A public-health message works best when it is:

   AWritten in precise clinical termsBHeld back until the outbreak endsCClear and tailored to its audienceDOne detailed version for the whole city

8. 8. A trustworthy public-health recommendation is:

   ABacked by evidenceBA message meant to frightenCOne expert's opinionDGuidance that ignores new data

9. 9. Public-health surveillance is used to:

   AProve a treatment works in a trialBTrack disease patterns to guide responseCDiagnose and treat one patientDMarket treatments to affected areas

10. 10. A restriction enzyme is used to:

    ACut DNA at a specific sequenceBRead the order of DNA basesCJoin two DNA fragments togetherDMake many copies of a DNA region

11. 11. DNA ligase's job in cloning is to:

    AOpen the plasmid at a restriction siteBCopy the insert before it is joinedCJoin the insert into the cut plasmidDBreak down leftover DNA in the tube

12. 12. Only transformed colonies grow on an antibiotic plate because the plasmid carries:

    AExtra nutrients the colonies useBA gene for antibiotic sensitivityCA gene that speeds up cell divisionDAn antibiotic resistance gene

13. 13. "Competent" cells are cells that:

    ACan take up DNA from outsideBSurvive the antibiotic alreadyCAlready carry the plasmid DNADCannot take in outside DNA

14. 14. In a controlled study, the control group provides:

    AA baseline for the treated groupsBThe outcome the study measuresCThe highest dose of the treatmentDThe variable the researcher changes

15. 15. Two variables rising together best supports:

    AThat the second variable causes the firstBA correlation, not proof of causeCThat the two measures are unrelatedDThat the first variable causes the second

16. 16. Contamination of a culture is best prevented by:

    ARinsing tools with tap waterBAseptic technique at each stepCWorking fast to limit air timeDOpening the plate to check growth

17. 17. You flame a wire loop until it glows red. It must cool before it touches your culture. A loop used too soon would:

    AKill off the cells you are trying to moveBStress the cells so they grow more slowlyCBreak down the antibiotic in the plateDPick up ash that the flame left behind

18. 18. Your streak plate grows colonies all over the surface, away from your streak lines. Plates from the same batch that you never streaked stayed clear. The likely source is:

    ABacteria that swam outward from the streak linesBA loop that was still dirty when you streakedCCells that settled from the air onto the agarDBad agar in the batch of plates you poured

19. 19. You streak a plate in four sections. You flame the loop and let it cool between sections. Each new section then receives:

    AFewer cells, so single ones land apartBA fresh supply of nutrients for growthCOne species per section, sorted by the loopDCells that the flame has already killed

20. 20. Two species both grow on one plate. One of them turns pink on it. That plate is:

    ASelective, since it holds back unwanted growthBDifferential, since two species can share the plateCDifferential, since one species looks differentDSelective, since the plate singles out one species

21. 21. Plates go into the incubator upside down. The agar then sits above the lid. Turning them over keeps:

    AWater drops off the growing surfaceBAir away from the cells on the plateCThe agar from drying out overnightDThe cells pressed onto their food

22. 22. A team takes three blood pressure readings from the same patient. Those three numbers mainly show:

    AHow much one patient's reading differs from another'sBThat a second team would measure the same valueCHow much that patient's own reading moves each timeDThat the study now includes three separate patients

23. 23. A team checks a balance against a known 100 g mass before use. This check:

    AShows whether the balance was zeroed before this sampleBRemoves the need to weigh each sample twiceCShows whether the balance can read smaller massesDShows whether the masses it reports can be trusted

24. 24. A graduated cylinder is marked every 1 mL. A student writes the volume as 24.85 mL. The problem with that written value is:

    AIt leaves off the plus or minus range for the readingBIt claims more precision than those marks can supportCIt reads the meniscus top instead of the bottomDIt estimates between the marks instead of reading them

25. 25. A step ran 20 minutes when the protocol said 10 minutes. The team should:

    ARecord the real 20 minutes and note it as a changeBEnter 10 minutes so the log matches the protocolCRecord 20 minutes and drop the run from the resultsDRecord 20 minutes and change the protocol to say 20

26. 26. A team tests a new stretch routine. One group is tested in the morning and the other after lunch. The design flaw is:

    ATime of day is the variable the team chose to testBTesting each group at a different time just adds noiseCEach group should have been tested on the same weekdayDTime of day changes along with the group being tested

27. 27. Your team has colonies growing on an ampicillin plate. Which check shows that a colony carries the insert?

    AGel bands after the colony's DNA is cutBHow many colonies grew on the plateCWhether the colony grows without ampicillinDHow well the colony grows on more ampicillin

28. 28. A team runs a restriction digest and the gel shows two bands. They forgot to load the ladder. From that gel they can still tell:

    AWhat the two pieces of DNA code forBWhich piece of DNA is the longer oneCHow many copies of DNA they loadedDThe size of each piece in base pairs

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