Microbial-technology

Fermentation:

1. Which of the following statements about bread making is correct?
   1. Bread is made with the help of ethanol fermentation.
      1. Bread dough has yeast in it, which carries out ethanol fermentation to release carbon dioxide. When the bread is baked, this carbon dioxide expands and makes the bread fluffy.

1. In ethanol fermentation, which entity does a pyruvate molecule lose to form acetaldehyde?
   1. CO2
2. In ethanol fermentation, how does pyruvate give rise to acetaldehyde?
   1. Decarboxylation
3. Because of which of the following reasons is lactic acid produced in lactic acid fermentation?
   1. Oxidation of NADH
      1. Lactic acid fermentation takes place when there isn’t enough oxygen to oxidize NADH by aerobic respiration.  NADH is oxidized instead by fermentation, the end products of which are lactic acid and NAD+
   2. Reduction of pyruvate
      1. At the last step of lactic acid fermentation, electrons from NADH are accepted by pyruvate. So, pyruvate gets reduced to form lactic acid.

1. In ethanol fermentation, what gets oxidized/reduced to form ethanol?
   1. Acetaldehyde gets reduced
      1. In ethanol fermentation, the product of glycolysis, pyruvate, gets converted to acetaldehyde. Acetaldehyde is an aldehyde, which is reduced to form an alcohol – ethanol.
2. Bread making is a process that is accomplished with the help of a microorganism. Which of the following are correct about bread making?
   1. Bread barely contains any alcohol.
      1. Alcohol is produced in bread dough from alcohol fermentation by yeast. However, most of this alcohol evaporates while the bread is baking, so only traces of it are left in bread.
   2. Bread is made using alcohol fermentation.
      1. Bread dough has yeast in it, which carries out alcohol fermentation and releases carbon dioxide. When the bread is baked, this carbon dioxide expands and makes the bread fluffy.

1. Lactic acid fermentation does not produce carbon dioxide. In lactic acid fermentation, lactic acid is the end-product. Which of the following lead to the production of lactic acid?
   1. Reduction of pyruvate
      1. At the last step of lactic acid fermentation, electrons from NADH are accepted by pyruvate. So, pyruvate gets reduced to form lactic acid.
   2. Oxidation of NADH
      1. Lactic acid fermentation takes place when there isn’t enough oxygen to oxidize the NADH by aerobic respiration. NADH is oxidized instead by fermentation, the end products of which are lactic acid and NAD+
2. Because of which of the following reasons is lactic acid produced in lactic acid fermentation?
   1. Reduction of pyruvate
      1. At the last step of lactic acid fermentation, electrons from NADH are accepted by pyruvate. So, pyruvate gets reduced to form lactic acid.
   2. Oxidation of NADH
      1. Lactic acid fermentation takes place when there isn’t enough oxygen to oxidize the NADH by aerobic respiration. NADH is oxidized instead by fermentation, the end products of which are lactic acid and NAD+

Cellular Respiration:

1. Which of the following happens in order to produce ethanol in ethanol fermentation?
   1. Acetaldehyde is reduced.
      1. In ethanol fermentation, the product of glycolysis, pyruvate, gets converted to acetaldehyde. Acetaldehyde is an aldehyde, which is reduced to form an alcohol – ethanol.
2. Match the columns for the different stages of cellular respiration and arrange the stages in the correct order of occurrence.

1. Different carbohydrates enter cellular respiration at different points. Which of the following options about the entry points of glycogen and fructose is correct?
   1. Both glycogen and fructose enter glycolysis at the investment phase.
2. A yeast cell is transported from an environment with oxygen to a completely oxygen-free environment. Which of the following answer choices are correct about the metabolic changes that will occur in the yeast cell?
   1. Glycolysis will still occur, followed by alcohol fermentation.
   2. Glycolysis will still occur, but the Krebs cycle and oxidative phosphorylation will stop
3. A toxic compound, fluoroacetic acid, disrupts the Krebs cycle.What would be the effect of fluoroacetic acid on cellular respiration overall?
   1. Glycolysis continues, oxidative phosphorylation stops, ATP production is markedly reduced.
4. Arrange the different stages of cellular respiration in the order in which they happen and match them with their respective reactions.

1. The following figure shows the two phases of the glycolytic pathway and two carbohydrate sources of energy: glycogen and fructose.

Glu – Glucose, Glyc – Glyceraldehyde-3-phosphate, Pyr – Pyruvate, I – Investment phase, II – Payoff phase, Gly – Glycogen, Fru – Fructose

1. Which of the following options correctly depict the entry points of glycogen and fructose into glycolysis?

1. Which of the following statements are true about cellular respiration in a yeast cell living in anaerobic conditions?
   1. It carries out glycolysis, which is followed by alcohol fermentation.
   2. It carries out glycolysis, but not the Krebs cycle or oxidative phosphorylation.

Microbes in human welfare:

Microbes and fermentation:

1. Neela wants to make bread at home. She makes a dough using flour and yeast, and leaves it undisturbed for an hour. When she comes back to it, the dough has doubled in size. Which of the following best explains why the dough has risen so much?
   1. Carbon dioxide produced by the yeast is trapped inside the dough, causing it to rise.
      1. The yeast breaks down sugars in the dough, during which carbon dioxide is produced. The gas gets trapped inside the dough, making it rise and increase in size.
2. Why is yogurt thicker than milk?
   1. Coagulated proteins in yogurt make it more solid than milk.
      1. The fermentation of milk into yogurt denatures milk proteins, which form a gel-like structure. This gives yogurt a more solid texture than milk.
3. Medha’s yogurt is almost over, so she decides to make some more. She adds the remaining spoon of yogurt to boiling milk, and leaves it undisturbed overnight. In the morning, however, she is upset to see that the milk has not turned into yogurt. Which of the following statements most likely explains why Medha’s yogurt failed to form?
   1. The milk was too hot when Medha added the remaining yogurt.
      1. The bacteria that ferment milk into yogurt need warm temperatures to survive and are killed or inactivated by high temperatures.
4. Which of the following statements about the production of cheese and yogurt are true?
   1. Both cheese and yogurt are made by fermenting milk.
      1. Production of both cheese and yogurt first requires milk to be acidified into lactic acid by fermentation.
   2. Unlike yogurt, cheese production involved separating the milk curds and whey.
      1. Fermented milk curdles into curds and whey. Cheese is produced by separating the curds from the whey and then processing them further. This separation does not happen in yogurt production.
5. Mani decides to make bread at home. He makes a dough with flour and water, but when he tries to bake it, the bread does not rise. After checking the recipe, Mani realizes that he forgot to add yeast. Which of the following statements best explains why yeast is needed in order to make bread rise?
   1. The yeast is needed to make carbon dioxide, which makes the dough rise.
      1. The yeast breaks down sugars in the flour, which produces carbon dioxide as a by product. The carbon dioxide gets trapped in air pockets inside teh dough, forcing it to rise.
6. Fermentation of milk by certain bacteria can produce yogurt. Interestingly, yogurt is much thicker in texture than the milk it was produced from. Which of the following statements best explains why yogurt is thicker than milk?
   1. Denatured proteins in yogurt give it a thicker consistency than milk.
      1. The fermentation of milk into yogurt denatures milk proteins, which form a gel-like structure. This gives yogurt a more solid texture than milk.
7. Malik’s yogurt is almost over, so he decides to make some more. He adds the remaining spoon of yogurt to warm milk, and leaves it overnight in the fridge. In the morning, however, he is upset to see that the milk has not turned into yogurt.Which of the following statements most likely explains why Malik’s yogurt failed to form?
   1. The milk was too cold to get fermented overnight into yogurt.
      1. The bacteria that ferment milk into yogurt need warm temperatures to work.
8. Both cheese and yogurt are made from milk. On the other hand, cheese has a range of flavors and textures, and can also take longer to make than yogurt. Which of the following statements best explain how these differences arise?
   1. Cheese does not contain whey.
      1. After fermenting milk to create lactic acid, it is curdled to separate the solid curds and watery whey. Unlike yogurt production, cheesemaking has an extra step to separate the curds from the whey.
   2. Cheese is often further processed with the help of other microbes.
      1. Sometimes, bacteria or fungi are added onto the surface of cheese. As the cheese ages, different microbes will add different flavors and textures to the cheese.
9. Which protein is the enzyme streptokinase likely to help break down?
   1. Fibrin, a protein which makes up blood clots
10. Saanvi loves making orange juice at home. But it always ends up being very cloudy.What can be added to fruit juice to make it clear?
    1. Pectinase
       1. Pectins are a constituent of plant cell walls and help contribute to making fruit juices murky. Pectinase is an enzyme that can break down pectins. So, pectinase can be added to fruit juice to make it clear.
    2. Protease
       1. Proteins interact with certain substances in plant cells, which makes fruit juices cloudy. Proteases can break down proteins. So, proteases can be added to fruit juice to make it clear.
11. A detergent-making company has decided to make its product more efficient in removing stains. The new improved detergent will have lipase as an added constituent. Which of the following stains would this detergent be most effective against?
    1. Ghee
       1. Ghee is a fat. Fats and oils belong to a category of biomolecules called lipids. Lipases are enzymes that can break lipids down. Hence, lipases can effectively remove ghee stains.
12. Myocardial infarction (heart attack) is treated by the enzyme streptokinase. Which phenomenon in myocardial infarction does streptokinase attack?
    1. Formation of blood clots in blood vessels
13. During the process of producing fruit juice, constituents of plant cell walls get mixed in the juice and produce cloudiness. Which enzymes are used to remove the cloudiness?
    1. Protease
       1. Proteins often interact with certain constituents of plant cells, which makes fruit juices cloudy. Proteases can break down these proteins. Hence, proteases can be used to reduce the cloudiness.
    2. Pectinase
       1. Pectins are an integral part of plant cell walls. During the production of fruit juices, some pectins get dissolved and cause cloudiness. Pectinases can catalyze the breakdown of pectins. Hence, pectinases can be used to reduce the cloudiness.
14. Which stains can detergents containing lipases easily get rid of?
    1. Butter
       1. Butter is made of fats. Fats belong to a category of biomolecules called lipids. Lipases are enzymes that catalyze the breakdown of lipids. Hence, lipases can remove butter stains.
15. The enzyme produced by Streptococcus will alleviate the symptoms of which disease?
    1. Deep vein thrombosis, in which legs are swollen and painful because of blood clots
16. The fruit juices produced in factories are much clearer than the ones we make at our homes. The reason is that they go through a clarification process, which involves several enzymes, including cellulases and amylases. What other enzymes are used to make cloudy juices clear?
    1. Protease
       1. Proteases can break proteins down. Proteins often cause fruit juices to be cloudy. So, proteases are used to make cloudy juices clear.
    2. Pectinase
       1. Pectinases break down pectins, which are constituents of plant cell wall and cause cloudiness during juice production. So, pectinases are used to make cloudy juices clear.

Applications in agriculture:

Bt crops and RNAi:

1. Genetically modified (GM) crops offer several advantages and disadvantages. Which of the following statements about GM crops are true?
   1. GM seeds are more expensive than non-GM seeds.
      1. The high costs of research and development of genetically engineered plants make GM seeds more expensive than non-GM seeds.
   2. Pests can develop resistance to toxins in GM crops.
      1. Pests can become resistant to GM crops (eg., pink bollworm resistance to Bt cotton), although there are ways to combat this (using combinations of genes, ‘reservoir’ crops, etc).
2. Bt technology is widely used to create plants with inbuilt bio-pesticides. From the list of statements below, identify the events that occur in Bt pest-resistance.
   1. Bt genes are inserted into the plant genome.
      1. The first step in Bt technology is to add target-specific genes from the bacterium Bacillus thuringiensis (Bt) to the plant genome.
   2. Gut pH of the pest activates toxins.
      1. Pests ingest inactive protoxins when they feed on Bt plants. The alkaline gut pH converts them into active toxins.
3. Mani plants three variants of Bt cotton in his field –  A few months later, the farm suffers from a serious cotton bollworm infestation and Mani takes note of the damage to the crops

1. Which of the following statements could explain Mani’s findings?
   1. Variant B, expresses the cryIAc gene.
      1. Bt toxins from the cryIAc gene make plants resistant to the cotton bollworm. Since variant B, was not damaged by the pest, it expresses cryIAc.
2. From the list of statements below, identify the events that form a part of RNA interference (RNAi).
   1. Agrobacterium vectors are used to genetically modify the plant .
      1. This is the first step of RNAi. Pest-specific genes are introduced into the plant using Agrobacterium vectors.
   2. Double stranded RNA (dsRNA) is formed in plant cells.
      1. Complementary sense and antisense RNA pair up to form double-stranded RNA (dsRNA), which initiates the RNAi process.
3. Genetically modified (GM) crops offer several advantages and disadvantages.Which of the following statements about GM crops is true?
   1. GM crops can be tailor-made to resist specific pests.
      1. GM crops are tailor-made. Target-specific genes are added to plants to give them resistance against those particular pests.
4. Bt technology is widely used to create plants with inbuilt bio-pesticides. From the list of statements below, identify the events that occur in Bt pest-resistance.
   1. Different crops have different cry genes inserted into their genomes.
      1. cry genes give target-specific resistance to plants. Cotton and brinjal plants, for example, need protection from different pests, and therefore need different cry genes.
   2. Bt toxins bind to the gut wall and cause lysis of epithelial cells.
      1. Bt toxins bind to epithelial cells in the gut wall, leading to formation of pores and ultimately death of the pest.
5. Sheela plants three variants of Bt corn in her field – A, B, and C. A few months later, the farm suffers from a serious corn borer infestation and Sheela takes note of the damage to the crops. Which of the following statements could explain Sheela’s findings?

1. Variant  B expresses the cryIAb gene.
   1. Bt toxins from the cryIAb gene make plants resistant to the corn borer. Since variant B was not damaged by the pest, it expresses cryIAb.
2. From the list of statements below, identify the events that form a part of RNA interference (RNAi).
   1. Pest-specific genes are introduced to the plant genome.
      1. This is the first step in RNAi. Pest-specific genes allow plants to recognise and silence that organism’s mRNA.
   2. Pest-specific genes produce complementary RNA strands.
      1. Complementary sense and antisense RNA pair up to form double-stranded RNA (dsRNA), which initiates the RNAi process.

Genetically engineered insulin:

1. A pharmaceutical company accidentally produces a batch of proinsulin, which cannot be sold. The company decides to convert this batch into mature insulin, which can then be sold. Which of the following steps can the company do take to convert their proinsulin into mature insulin?
   1. Remove peptide
      1. Peptide C is present only in proinsulin. Removing it will convert proinsulin into mature insulin. The company should take this step.
2. Insulin isolated from animals like pigs was used to treat diabetes in the past, but genetically engineered (GE) insulin has become more common in recent times. Which of the following statements about these two methods of sourcing insulin are true?
   1. GE insulin can be produced in larger quantities.
      1. Several million bacteria can each be made to produce human insulin via genetic engineering. This produces much larger quantities than insulin extracted from animals like pigs.
3. A new oral insulin pill hits the market, but is soon found to be very ineffective compared to the standard method of injecting insulin. Which of the following statements could most likely explain why the pill was ineffective?
   1. Oral insulin gets degraded.
      1. Insulin is a peptide, and the stomach and gut digest peptides. Oral insulin will get degraded before it can affect blood glucose levels, and so can be ineffective as treatment.
4. A scientist mixes different peptides together to try and create mature insulin. The table below lists the combinations she tried for each experiment:

1. Which of the above experiments would have succesfully produced mature insulin?
   1. Experiment 3
      1. Peptide C is only present in proinsulin and not in mature insulin. Since mature insulin only contains peptides A, B this experiment would have succeeded.
2. Which of the following are advantages of genetically engineered (GE) human insulin over insulin isolated from animals?
   1. Lower chance of immune reactions.
      1. Unlike animal insulin, genetically engineered human insulin matches the natural peptide found in our bodies perfectly, and so is less likely to trigger immune reactions in diabetics.
   2. Higher quantity of insulin produced.
      1. Several million bacteria can each be made to produce human insulin via genetic engineering. When compared to the amount of insulin isolated from animals, the GE method results in much higher quantities of insulin produced.
3. Several companies have researched or tested oral insulin pills, but have failed to bring out a successful product. Instead, the most popular product on the market are different forms of insulin injections. Why is oral insulin not commonly sold or administered to diabetics?
   1. Insulin gets digested when taken orally.
      1. Insulin is a peptide, which quite literally gets digested by the stomach and gut. This is why insulin is usually administered through injections, and not orally.
4. A pharmaceutical company accidentally produces a batch of proinsulin, which cannot be sold. The company decides to convert this batch into mature insulin, which can then be sold. Which of the following steps can the company do take to convert their proinsulin into mature insulin?
   1. Remove peptide C.
      1. Peptide C is present only in proinsulin. Removing it will convert proinsulin into mature insulin. The company should take this step.
5. Insulin isolated from animals like pigs was used to treat diabetes in the past, but genetically engineered (GE) insulin has become more common in recent times. Which of the following statements about these two methods of sourcing insulin are true?
   1. GE insulin can be produced in larger quantities.
      1. Several million bacteria can each be made to produce human insulin via genetic engineering. This produces much larger quantities than insulin extracted from animals like pigs.
6. Which of the following are advantages of genetically engineered (GE) human insulin over insulin isolated from animals?
   1. Higher quantity of insulin produced.
      1. Several million bacteria can each be made to produce human insulin via genetic engineering. When compared to the amount of insulin isolated from animals, the GE method results in much higher quantities of insulin produced.
   2. Lower chance of immune reactions.
      1. Unlike animal insulin, genetically engineered human insulin matches the natural peptide found in our bodies perfectly, and so is less likely to trigger immune reactions in diabetics.

Gene therapy:

1. Pramod is diagnosed with adenosine deaminase (ADA) deficiency. In order to treat him, doctors harvest his lymphocytes, and alter them using genetic engineering. The lymphocytes are then returned to Pramod’s body. How are the lymphocytes altered in order to treat Pramod’s ADA deficiency?
   1. A functional ADA gene is inserted into the lymphocytes.
      1. A correct copy of the ADA gene is inserted into the lymphocytes, which then allows them to express the enzyme. Thus, this gene therapy allows Pramod to recover from his ADA deficiency as long as he has a supply of the altered lymphocytes.
2. A doctor diagnoses a young child with adenosine deaminase (ADA) deficiency. He meets with the parents of the child, and explains to them that this disorder causes immunodeficiency. Which of the following explanations would the doctor have most likely given to the parents?
   1. The disorder is caused by a lack of ADA enzyme.
      1. The ADA enzyme normally breaks down adenosine or deoxyadenosine. Without this enzyme, toxic levels of its substrate build up inside cells and ultimately kill them. The doctor would have most likely given this explanation to the parents
   2. This disorder causes a lack of lymphocytes.
      1. ADA deficiency causes the excessive build up of adenosine or deoxyadenosine in lymphocytes, which ultimately kills them. Since lymphocytes are immune cells, this leads to immunodeficiency. The doctor would have most likely given this explanation to the parents.
3. Scientists have developed gene editing technologies that can one day help permanently cure adenosine deaminase (ADA) deficiency. Which of the following could be one such example of a cure for ADA deficiency?
   1. Adding the ADA gene into cells of developing embryos.
      1. Humans develop from a single cell, which divides to give rise to two cells, four cells, and so on. Adding the ADA gene into early embryonic stages (like the single-cell stage) ensures that all cells that form from subsequent divisions will have a copy of the gene.
         1. Therefore, this is an example of a permanent cure for ADA deficiency.
4. Meera suffers from adenosine deaminase (ADA) deficiency, and needs to get injections of ADA every 3-4 days. Why can’t Meera just get a single shot of ADA, instead of needing frequent injections?
   1. Meera’s ADA enzyme levels need to be regularly topped up.
      1. ADA deficiency is caused by a genetic inability to produce enough ADA. While ADA can be introduced to the body through injections, this is only temporary since the enzyme gets degraded after a few days.
      2. So, Meera needs to get frequent injections and can’t just get one shot of ADA.
5. Stella is diagnosed with adenosine deaminase (ADA) deficiency. Her doctors recommend gene therapy as treatment, for which they collect Stella’s lymphocytes from her body. Using genetic engineering, they alter the lymphocytes and then pump them back into Stella’s body. How were Stella’s lymphocytes altered in order to treat her ADA deficiency?
   1. A functional ADA gene was inserted into Stella’s lymphocytes.
      1. During gene therapy, a correct copy of the ADA gene is inserted into the lymphocytes, which then allows them to express the enzyme. Thus, Stella’s lymphocytes were altered to prevent ADA deficiency by producing ADA from the functional gene inserted into them.
6. Adenosine deaminase (ADA) deficiency is usually detected in young children within the first two years of life, who usually suffer from widespread rashes, pneumonia, and frequent ear infections. These issues are due to poor immune function caused by ADA deficiency. Which of the following statements help explain how ADA deficiency leads to immunodeficiency?
   1. ADA deficiency prevents the breakdown of toxic substances.
      1. The ADA enzyme normally breaks down adenosine or deoxyadenosine. Without this enzyme, toxic levels of its substrate build up inside immune cells and ultimately kill them.
   2. This disorder causes low levels of lymphocytes and natural killer cells.
      1. ADA deficiency causes the excessive build up of adenosine or deoxyadenosine in lymphocytes and natural killer cells, which ultimately kills them. Since these are immune cells, this leads to immunodeficiency.
7. Similarly, other types of stem cells can be targeted with new developments in genetic engineering. Which of the following is an example of how genetic engineering can be used to target stem cells and permanently cure ADA deficiency?
   1. Adding the ADA gene into developing embros.
      1. Humans develop from a single cell (or embryonic stem cell), which divides to give rise to two cells, four cells, and so on. Adding the ADA gene into early embryonic stages (like the single-cell stage) ensures that all cells that form from subsequent divisions will have a copy of the gene.
      2. Therefore, this is an example of a permanent cure for ADA deficiency.
8. Patients (usually young children) who suffer from adenosine deaminase (ADA) deficiency can be treated with enzyme replacement therapy. Children undergoing this treatment receive weekly or biweekly injections of the ADA enzyme. Which of the following statements best explains why the treatment needs to be taken so frequently?
   1. Enzyme levels drop within a few days, and so need to be regularly replaced.
      1. ADA deficiency is caused by a genetic inability to produce sufficient levels of the ADA enzyme. Enzyme replacement therapy temporarily introduces ADA into the body, but levels of the enzyme drop after a few days as the body degrades it. So, the treatment needs to be taken every few days in order to keep levels of ADA sufficient.

Molecular diagnosis:

1. A woman with suspected human papillomavirus (HPV) undergoes a smear test. Sample tissue from the smear is tested using polymerase chain reaction (PCR). The test comes back positive for HPV. Which of the following statements best explain what this diagnosis means?
   1. The PCR detected viral DNA.
      1. PCR tests can detect and amplify specific DNA sequences. The positive test result means that the PCR was able to find DNA sequences specific to HPV in the sample, which indicates an infection.
2. Scientists want to study tissue samples from patients diagnosed with prostate cancer. Using autoradiography, they are able to detect the presence of a specific, prostate cancer tumor marker in these samples. How did this technique detect the tumor marker in the tissue samples?
   1. It used a probe to detect the tumor marker proteins.
      1. Autoradiography uses probes with complementary sequences to bind and detect its target. The tissue samples were treated with radioactive probes against the tumor marker protein, and then exposed to film.
      2. Radioactive signals from the marker-probe complex were detected on the film, which indicated the presence of the tumor marker.
3. A patient with recurring infections gets a blood test. The blood sample is tested for viruses using enzyme-linked immunosorbent assay (ELISA). The attending doctor wishes to check specifically for the presence of human immunodeficiency virus (HIV) in this patient. How can ELISA be used to test for HIV?
   1. It can detect antibodies against HIV.
      1. ELISA checks if the plasma in blood samples contain antibodies against specific pathogens. HIV-positive patients will have antibodies against the virus. ELISA can be used to detect anti-HIV antibodies, which, in turn, indicates the presence of the HIV virus.
4. After an anthrax scare, a farmer gets a blood test done to check for infection. The blood is tested using polymerase chain reaction (PCR). The test comes back positive for the presence of anthrax-causing bacteria, Bacillus anthracis. Which of the following statements best explain what this diagnosis means?
   1. The PCR detected bacterial DNA.
      1. PCR tests can detect and amplify specific DNA sequences. The positive test result means that the PCR was able to find DNA sequences specific to Bacillus anthracis, which indicates an anthrax infection.
5. Scientists want to study brain tissue samples from patients who died with Alzheimer’s disease (AD). They test the samples for differences with non-AD brains using autoradiography. The test results show that AD brains have fewer receptors for a type of neurotransmitter. How could autoradiography detect the reduced number of receptors in AD brains?
   1. It uses a probe to detect the receptor. Autoradiography uses probes with complementary sequences to bind and detect its target. In this case, the brain tissue is treated with radioactive probes against the receptor, and then exposed to film. The radioactive signals from the receptor-probe binding will be detected on the film, which can be compared with those from non-AD brains to check for receptor distribution.
6. A patient gets a blood test to check for sexually transmitted diseases. The blood sample is tested for various pathogens using enzyme-linked immunosorbent assay (ELISA). The test comes back positive for Treponema pallidum, the bacterium which causes syphilis. How did the test detect syphilis in the patient?
   1. It detected antibodies against Treponema pallidum. ELISA checks if the plasma in blood samples contain antibodies against specific pathogens. Syphilis-positive patients will have antibodies against Treponema pallidum. ELISA detected antibodies against this bacterium, which indicates the presence of the Treponema pallidum, or a syphilis infection.
7. A woman with suspected human papillomavirus (HPV) undergoes a smear test. Sample tissue from the smear is tested using polymerase chain reaction (PCR). The test comes back positive for HPV. Which of the following statements best explain what this diagnosis means?
   1. The PCR detected viral DNA.
      1. PCR tests can detect and amplify specific DNA sequences. The positive test result means that the PCR was able to find DNA sequences specific to HPV in the sample, which indicates an infection.
8. Scientists want to study tissue samples from patients diagnosed with prostate cancer. Using autoradiography, they are able to detect the presence of a specific, prostate cancer tumor marker in these samples. How did this technique detect the tumor marker in the tissue samples?
   1. It used a probe to detect the tumor marker proteins.
      1. Autoradiography uses probes with complementary sequences to bind and detect its target. The tissue samples were treated with radioactive probes against the tumor marker protein, and then exposed to film. Radioactive signals from the marker-probe complex were detected on the film, which indicated the presence of the tumor marker.
   2. It checked for the tumor marker sequence.
      1. Autoradiography uses probes with complementary sequences to bind and detect its target. In this case, radioactive DNA probes against the tumor marker were used to bind to the sequence, and then detected using film.