Revisiting lactose intolerance (from Ch. 3) (part III) • Biosphere Ecosystem/Biome Community Population Organism Organs and organ system Tissue Cell Organelle Molecule: DNA Revisiting lactose intolerance − In lactase persistent people, lactase gene is on and transcribed and lactase is produced via translation − Review lactose tolerance/lactase persistence (also see Ch. 3, sect. 17) − How can lactose intolerance be diagnosed? − Let’s look at data from: blood glucose test and H test − Analyze results from blood glucose tests − Draw graph from H tests and analyze results Review: Lactase persistence (review outside of class: scroll down and click ‘watch on YouTube’) • We now know that genes code for proteins and these proteins are made via t__________ and t_________ – In mammals, lactase gene is transcribed and __________ is made via translation • However, in most adult mammals, gene is turned off in adulthood – Results: • But, in lactase persistent people, gene remains turned on (due to a mutation associated with gene) – “lactase persistent” = lactose tolerant – Meaning: Work with a buddy. Read text on 2 slides and answer questions 1-6. Questions: lactose and lactase persistence 1. Define lactose intolerance. 2. What typically happens to the expression of the lactase gene when a baby is weaned from his or her mother’s milk? 3. What type of carbohydrate is lactose? What 2 simple sugars make up lactose? 4. In lactose tolerant people, where in the digestive system is lactase produced (and therefore the monosaccharides that make up lactose absorbed)? 5. What causes bloating when a person who is lactose intolerant drinks milk? 6. Define lactase persistence. Lactase persistence (at 3:05 min) • 1 test for lactose tolerance: blood glucose test – If lactose can be hydrolyzed, draw a line indicating how levels of blood glucose levels are expected to change after consumption of milk blood glucose time – Now, draw a line (of a different color) indicating how levels of blood glucose are expected to change, for a person who is lactose intolerant Activity analyzing scientific data: blood glucose levels Data below show blood glucose levels of 6 individuals tested in Dr. Tishkoff’s lab. After baseline (i.e., time 0 min) blood glucose levels were measured and recorded, each person drank 1L milk. Blood glucose levels were again measured at 15, 30, 45, and 60 min after drinking milk. Glucose levels were measured using glucose strips and a glucose reader similar to the one Dr. Wells used in film associated with weblink on last slide. Plot data above in graph on next slide. Graph already includes Spencer’s blood glucose test results. Questions: Blood glucose data 1. Why is measuring blood glucose levels an indicator of someone’s lactase activity? It is important because it shows if an individual has the lactase gene turned on or not. If someone has an increase of blood glucose, then they have the ability to produce lactase. 2. Divide the 7 people into 2 groups (A and B), based on their blood glucose test results. Write the names of the people in each group, including Dr. Wells. • Group A: Lactose Intolerant: Katherine, Arthur, Rachel • Group B: Lactose Tolerant: Everyone else 3. Explain your rationale for dividing the people into these 2 groups, using data to support your answer. I divided these people up into two groups due to either their tolerance or intolerance to lactose which is causes by either having or not having the lactose gene turned on. If the lactose gene is turned on, then that person can produce lactase - the enzyme/protein that is needed to break down lactose which is found in milk. Questions: Blood glucose data 4. Based on these data, do you predict that individuals in Group A are lactase persistent or nonpersistent? Describe the evidence that supports this claim. Lactase nonpersistent because they cannot consume lactose becasue their gene turned off. 5. Based on these data, do you predict that individuals in Group B are lactase persistent or nonpersistent? Describe the evidence that supports this claim. Lactase persistent becasue their lactose gene persisted to stay on, giving them the ability to break down lactose. 6. If you performed the same blood glucose test on people from the Maasai population in Kenya, predict whether their results would be more like those of Group A or Group B. Explain your prediction. (Hint: Maasai people raise cattle.) I perdict that the results would be like group B, and would be generally lactase persistent because this population of people commonly raises cattle. Therefore, keeping the ability to drink milk would be extremely beneficial to their society. Questions: Blood glucose data 7. Let’s revisit the condition of diabetes. Recall the oral glucose tolerance test which measures blood glucose concentration before and 2 hours after drinking a sweet drink, which indicates how body processes glucose. For this test, after 2 hours: − < 140 mg/dL: normal (70-99: normal fasting blood sugar) − > 200: diabetes − 140-200: prediabetic Compare that graph on the next slide with the graph you just made. Does anyone seem to have pre-diabetes or diabetes in the graph you made? Justify your answers. Three of these people including Dr. Wells are Prediabetic - meaning that they have blood glucose levels of 140-200 after drinking the milk. Blood glucose (mg/100 mL) From our discussion of insulin and diabetes (ch. 4) 400 350 Person A 300 250 200 150 Person B 100 50 0 0 1 2 1 2 3 Hours after glucose ingestion 4 5 H breath test: another test of lactase persistence Draw a graph below using the data. Be sure to include labels for your X and Y axes. Dan and Cindy obviously have lactase inpersistnence becasue they have high levels of hydrogen in their breath which means that they are fermenting the lactose that they just consumed in their large intestine. Questions: Hydrogen breath test data 1. Which individuals appear to be lactase persistent? Use data to support your answer. Dan and Cindy because they have high levels of hydrogen 2. Which individuals appear to be lactase nonpersistent? Use data to support your answer. Everyone else, because they have low levels of hydrogen Answer the exam review questions that correspond to this lecture now, so you can begin mastering the concepts and ace the exam.
