Do Q1 Applying concepts both part a as well as b Inquiry & AnalysisWhy Do Human Cells Age?Effect of Telomerase on Cell Culture GrowthPopulation doublingsHuman cells appear to have built-in life spans. As you learned306090120150in this chapter, cell biologist Leonard Hayflick reported in 1961the startling result that skin cells growing in tissue culture,such as those growing in culture flasks in the photo below, willNormalTelomerase plusdivide only a certain number of times. After about 50 populationdoublings, cell division stops (a doubling is a round of celldivision producing two daughter cells for each dividing cell;for example, going from a population of 30 cells to 60 cells).If a cell sample is taken after 20 doublings and frozen, whenthawed, it resumes growth for 30 more doublings and thenstops. An explanation of the "Hayflick limit" was suggested in1978, when researchers first glimpsed an extra length of DNAat the end of chromosomes. Dubbed telomeres, these lengthsproved to be composed of the simple DNA sequence TTAGGG,0 3 6 9 12 15 18 21 24 2730 33repeated nearly a thousand times. Importantly, telomeresMonthsTTAGGG TTAGGG TTAGGG TTAGGG TTAGGG---were found to be substantially shorter in the cells of olderbody tissues. This led to the hypothesis that a run of some16 TTAGGGS was where the DNA replicating enzyme, calledpolymerase, first sat down on the DNA (16 TTAGGGS beingthe size of the enzyme's "footprint"), and because of being itsdocking spot, the polymerase was unable to copy that bit. Thus,a 100-base portion of the telomere was lost by a chromosomeduring each doubling as DNA replicated. Eventually, after some50 doubling cycles, each with a round of DNA replication, thetelomere would be used up and there would be no place for theDNA replication enzyme to sit. The cell line would then entersenescence, no longer able to proliferate.This hypothesis was tested in 1998. Using geneticengineering, researchers transferred into newly establishedCourtesy Priv. Doz. Dr. Roland Zelhuman cell cultures a gene that leads to expression of anenzyme called telomerase that all cells possess but no bodyb. After how many doublings do the telomerase pluscell uses. This enzyme adds TTAGGG sequences back to thecells cease to divide in this experiment?end of telomeres, in effect rebuilding the lost portions of thetelomere. Laboratory cultures of cell lines with (telomerase3. Making Inferences After nine population doublings,would the rate of cell division be different between theplus) and without (normal) this gene were then monitored fortwo cultures? After 15? Why?many generations. The graph displays the results.4. Drawing Conclusions How does the addition of theAnalysistelomerase gene affect the senescence of skin cellsgrowing in culture? Does this result confirm the telomerase1. Applying Conceptsa. Variable. In the graph, what is the dependent variable?b. Comparing Continuous Processes. How do normalskin cells (blue line) differ in their growth history fromtelomerase plus cells with the telomerase gene (red line)?hypothesis this experiment had set out to test?5. Further Analysisa. Cancer cells are thought to possess mutationsdisabling the cell's ability to keep the telomerase geneshut off. How would you test this hypothesis?2. Interpreting Dataa. After how many doublings do the normal cells cease todivide? Is this consistent with the telomerase hypothesis?b. Sperm-producing cells continue to divide throughouta male's adult life. How might this be possible? Howwould you test this idea?Relative growth rate

Question

Do Q1 Applying concepts both part a as well as b Inquiry & AnalysisWhy Do Human Cells Age?Effect of Telomerase on Cell Culture GrowthPopulation doublingsHuman cells appear to have built-in life spans. As you learned306090120150in this chapter, cell biologist Leonard Hayflick reported in 1961the startling result that skin cells growing in tissue culture,such as those growing in culture flasks in the photo below, willNormalTelomerase plusdivide only a certain number of times. After about 50 populationdoublings, cell division stops (a doubling is a round of celldivision producing two daughter cells for each dividing cell;for example, going from a population of 30 cells to 60 cells).If a cell sample is taken after 20 doublings and frozen, whenthawed, it resumes growth for 30 more doublings and thenstops. An explanation of the &#34;Hayflick limit&#34; was suggested in1978, when researchers first glimpsed an extra length of DNAat the end of chromosomes. Dubbed telomeres, these lengthsproved to be composed of the simple DNA sequence TTAGGG,0 3 6 9 12 15 18 21 24 2730 33repeated nearly a thousand times. Importantly, telomeresMonthsTTAGGG TTAGGG TTAGGG TTAGGG TTAGGG---were found to be substantially shorter in the cells of olderbody tissues. This led to the hypothesis that a run of some16 TTAGGGS was where the DNA replicating enzyme, calledpolymerase, first sat down on the DNA (16 TTAGGGS beingthe size of the enzyme's &#34;footprint&#34;), and because of being itsdocking spot, the polymerase was unable to copy that bit. Thus,a 100-base portion of the telomere was lost by a chromosomeduring each doubling as DNA replicated. Eventually, after some50 doubling cycles, each with a round of DNA replication, thetelomere would be used up and there would be no place for theDNA replication enzyme to sit. The cell line would then entersenescence, no longer able to proliferate.This hypothesis was tested in 1998. Using geneticengineering, researchers transferred into newly establishedCourtesy Priv. Doz. Dr. Roland Zelhuman cell cultures a gene that leads to expression of anenzyme called telomerase that all cells possess but no bodyb. After how many doublings do the telomerase pluscell uses. This enzyme adds TTAGGG sequences back to thecells cease to divide in this experiment?end of telomeres, in effect rebuilding the lost portions of thetelomere. Laboratory cultures of cell lines with (telomerase3. Making Inferences After nine population doublings,would the rate of cell division be different between theplus) and without (normal) this gene were then monitored fortwo cultures? After 15? Why?many generations. The graph displays the results.4. Drawing Conclusions How does the addition of theAnalysistelomerase gene affect the senescence of skin cellsgrowing in culture? Does this result confirm the telomerase1. Applying Conceptsa. Variable. In the graph, what is the dependent variable?b. Comparing Continuous Processes. How do normalskin cells (blue line) differ in their growth history fromtelomerase plus cells with the telomerase gene (red line)?hypothesis this experiment had set out to test?5. Further Analysisa. Cancer cells are thought to possess mutationsdisabling the cell's ability to keep the telomerase geneshut off. How would you test this hypothesis?2. Interpreting Dataa. After how many doublings do the normal cells cease todivide? Is this consistent with the telomerase hypothesis?b. Sperm-producing cells continue to divide throughouta male's adult life. How might this be possible? Howwould you test this idea?Relative growth rate

Accepted Answer

In graph, independent variable belongs to the x-axis on the graph (horizontal line). The dependent…

1. Applying Concepts a. Variable. In the graph, what is the dependent variable? b. Comparing Continuous Processes. How do normal skin cells (blue line) differ in their growth history from telomerase plus cells with the telomerase gene (red line)?