Bio 101 Lab Assignment 3Molecular Weight of DNAPoints: 40

Though lab work is shared between partners, lab assignments should be prepared on your own.

Do not share your lab assignment with anyone else in class before it was graded.

To begin this assignment, include your name, section number and date in the upper-left corner of the paper. Turn in a hard copy on the due date. Do not email or turn in through Blackboard.

Keep font size 12, double spaced. Multiple pages must be stapled.

Molecular Weight of DNA (p 195)

You should have three headings in bold justified to left. They are: Purpose, Results and Conclusion.

  1. Describe the purpose of this lab exercise in your own words.

(in the first paragraph)What is meant by molecular weight of DNA? What are the units of this measurement?

(in the second paragraph) Explain how molecular weight of a DNA fragment of an unknown size is estimated. What is the relationship between mol weight of a DNA fragment and the distance migrated by that fragment in an agarose gel. (do NOT copy the information from the lab manual, text book or web sites). Resources must be used only to get an idea and help you develop the best descriptive purpose in as few words as possible.

(in the third paragraph) Write the purpose of this lab in past tense.

  1. Give the Resultsin 2 tables and one figure

Table 1: Give the table on p 196 that has the size of the molecular weight standard and the distance travelled. Give an appropriate descriptive title above the table.

Figure 1. Prepare the figure. Instructions to prepare this figure are given at the end of this document. (Alternatively, you can work from the blank figure posted in a separate file.) Be sure to label the axes with units, and clearly label the 3 vertical and horizontal lines that correspond to fragments A, B and C. Give a suitable title below the graph.

Table 2. This is the results table given in the bottom of page 196. Include the sizes of the 3 fragments that you estimated from the standard curve figure.

  1. Conclusion

Write a brief conclusion, addressing your purpose and the method. Give your findings. Which band (A, B or C) has the greatest mol weight? The least mol weight?

*** Remember your quality of writing is assessed in this and all other writing assignments.

Late submission: -4 pts each lab period late. Lab assignments are not accepted after 1 wk of due date.

How to make the graph in Excel:

  1. Open up Excel spread sheet.
  2. Create a table for data in table 1. Add column headings Distance travelled (cm) to A1 and Molecular weight of Standard (in kb), to B1. (Make sure distance comes before Mol wt)
  3. Add Distance travelled data from your Table 1 (on page 196 in lab book) to cells A2-A11. Add molecular weight data to cells B2-B11.
  4. Highlight columns A1-A11 and B1-B11 and choose Insert from the top menu, and insert a Scatter. Then choose Scatter.
  5. You will see your data points on a curve, they are not connected yet.
  6. To get the Y axis on log scale, right click on the Y axis of the graph and select Format Axis and click Logarithmic scale. At this time, data points will be on a more or less a straight line but they are still not connected. Notice how the X axis jumped to the middle of the graph.
  7. In order to move the X axis to the bottom of the graph, right select X axis and choose Format axis, then Axis label, then Low.
  8. In order to get grid lines, right select X axis and choose Format grid lines, then Add minor grid lines,
  9. Do the same for the Y axis. This should add all grid lines.
  10. To get the straight line through the data points, right click on one of the data points, select AddTrend Line, then select Exponential. This should give you a nice straight line through data points.
  11. To add axis labels: Go to Layout, then choose Axis titles, Primary Horizontal Axis, Title Below Axis. This will make a text box appear below the X axis. Label this axis.
  12. Then do Y axis the same way. Go to Layout, then Axis titles, Primary Vertical Axis, Rotated tile. Label this axis and give the units.
  13. Click on Molecular weight title on the top and delete this. Instead of this, type a figure heading in Word as the rest of your lab report.
  14. Save and print the figure. Do the rest by hand using three colors of markers.