Writing Lab Report 1
Standard Curve Analysis
for DNA Quantitation
Contents of Lab Report 1
Cover Page
 Results
Text
Two Figures (graphs) with proper captions
One Table with a proper caption
Discussion
For each figure and table provide a(n)
Data Analysis
Error Analysis
Conclusion identifying the relationships
observed in the data analysis
Cover Page
Your name
Names of your lab partners
Lab Section
Date
Results: Text
 Briefly describe what each figure and table
represents
 introduce the reader to the order in which you are
presenting the data
 use an objective description that explains what you
expect the reader to notice about the data
 do not interpret the data in this section
 do not provide error analysis
 You may briefly explain the pattern observed
in the data and/or refer to the relationship
indicated by the shape of each graph. Use the
descriptions in the Lab Manual section “How
to Write a Scientific Report” pages 11-12.
Results: Figure 1
 Use Excel to plot the absorbance values at each
concentration for YOUR GROUP’S data
 Superimpose a smooth trendline
 Record the equation of the trendline to present
in the caption and use in calculations for Table 1
 Label the axes appropriately, indicating the x
and y variables and their units of measure
Also for Figure 1
Provide a caption below the figure
title
brief description, that can include
source of the data
relationship observed, including
equation for trendline
how the figure will be used in the
results and/or discussion sections
Example of Figure 1 with Dr. Colavito’s Data
Obtained in Summer 2010
1.6
Label (units)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
0.002
0.004
0.006
Label (units)
0.008
0.01
0.012
Example of Figure 1 with Data Obtained in Summer 2010
Adding a Trendline
1.6
Label (units)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
0.002
0.004
0.006
0.008
0.01
Label (units)
Be sure to copy the trendline equation and save it to use later.
For the line on this grapy: y = 145.52x - 0.0793; R2 = 0.9849.
0.012
Example of Figure 1 with Data Obtained in Summer 2010
Adding a Caption
I am the title of this
PowerPoint slide,
not the title of the
graph. Do not copy
my format in your
lab report!
1.6
Label (units)
1.4
1.2
1
I am the description
for this figure caption.
Yours will be more
specific to the
experiment you
performed, of course.
0.8
0.6
0.4
0.2
0 for this
I am the title
0 my 0.002
figure. Follow
format but use your
own words.
0.004
0.006
0.008
0.01
0.012
Label (units)
Figure 1: Standard Curve of Methylene Blue Absorbance. Absorbance
values were obtained for dilutions of a 0.01% methylene blue solution.
The equation for the trendline is y = 145.52x - 0.0793; R2 = 0.9849.
Results: Figure 2
 For CLASS DATA, use Excel to plot the mean
values for absorbance at each concentration
 Superimpose a smooth trendline
(reporting the equation for this trendline is optional)
 Use the standard deviation values for Vertical
(Y) error bars
 Label the axes appropriately, indicating the x
and y variables and their units of measure
 Provide a caption below the figure, including
Title
Brief description
Example of Figure 2 with Data
Obtained in Summer 2010
1.4
1.2
Label (units)
1
0.8
0.6
0.4
0.2
0
0
0.002
0.004
0.006
Label (units)
0.008
0.01
0.012
Example of Figure 2 with Data Obtained in Summer 2010
Adding Error Bars
1.6
1.4
Label (units)
1.2
1
0.8
0.6
0.4
0.2
0
0
0.002
0.004
0.006
0.008
0.01
0.012
Label (units)
Each error bar shows the range of +1SD from the mean value.
Results: Table 1
 Determine the total yield of YOUR DNA
EXTRACTION and show the process by providing the
information for Columns
2-7 from Table 2 in the lab instructions
 Use any table format that clearly shows the results
 Showing the calculations is optional
 Provide a caption above the table, including
 Title
 Brief Description: This description should include
the calculated value of the mean + 1 standard
deviation for DNA Yield, using the class data.
Data to present in Table 1
(taken from Table 2 of Lab Instructions)
2
3
4
5
6
7
Weight
(g)
Abs550 for
Methylene
Blue-stained
DNA solution
Concentration
of Solution (%)
(from standard
curve)
Concentration of
DNA
(micrograms/mL)
Total Amount of
DNA Recovered
(micrograms)
DNA Yield
(micrograms
DNA/gram
strawberry)
25
1.1
Absorbance reading
for 5 mL solution
containing methylene
blue-stained DNA
from one strawberry
DNA extraction
Using the Standard Curve in Figure 1 to determine the percentage
of methylene blue corresponding to the DNA solution
1.6
Label (units)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
0.002
0.004
0.006
0.008
0.01
Concentration of Methylene Blue (%)
Substitute 1.1 for the y value in the trendline equation:
y = 145.52x - 0.0793; x=0.0081%
0.012
Data to present in Table 1
(taken from Table 2 of Lab Instructions)
2
3
4
5
6
7
Weight
(g)
Abs550 for
Methylene
Blue-stained
DNA solution
Concentration
of Solution (%)
(from group’s
standard curve)
Concentration of
DNA
(micrograms/mL)
Total Amount of
DNA Recovered
(micrograms)
DNA Yield
(micrograms
DNA/gram
strawberry)
25
1.1
0.008
0.70
3.5
0.14
For Column 5: Use conversion factor shown below:
0.001%
= 0.0081%
Z = 0.70 micrograms/milliliter
0.086 micrograms/milliliter
Z
For Column 6: Correct for 5 ml total volume.
0.70 micrograms/milliliter x 5 milliliters = 3.5 micrograms
For Column 7: Divide by the starting weight of the strawberry.
3.5 micrograms/25 grams = 0.14 micrograms DNA/grams strawberry
Discussion: Data Analysis
 See Lab Manual Instructions for specific
questions to consider in analyzing the data
 For Figure 1, state the line/curve shape that you
proposed and then explain WHY the line/curve
would be this shape. Be sure to consider the
mathematical relationship illustrated by the
line/curve shape. Your goal is to address the
MECHANISM by which this relationship occurs.
 For Figure 2, discuss how well the data fit the
proposed line/curve. Does the range shown by
the data points + error bars overlap the best fit
line? If your data fit the proposed line/curve
shape, TENTATIVELY accept the mechanism as
an explanation for the observed relationship.
Discussion: Data Analysis
For Table 1, consider the usefulness of the
standard curve in quantifying the DNA
extracted from strawberries. Address the
specificity of the protocol in isolating DNA.
Describe whether your individual DNA yield
is reasonable in comparison to the class
data.
Discussion: Error Analysis
 Be BRIEF
 Suggest sources that match both the direction
and magnitude of the error
 If deviation of data points from the curve or line is
not large, do NOT suggest major sources of error.
 At least two sources of error should be
identified, one should be systematic error, the
other should be intrinsic (random) error
 Indicate which sources of error are specific to
each figure/table presented
Conclusion
Write one (or a few) brief statement(s)
that summarizes the relationship(s)
observed between the variables that you
studied
Comment on the variation observed for
the class data
Collaboration
 You may DISCUSS any aspects of your lab
report with fellow students and/or your
instructor
 You must PRODUCE the figures and WRITE
your lab report independently
 Any unusual similarities will be addressed
according to the SMC Code of Academic
Conduct. Everyone involved will lose full credit
for their reports. There are no makeups for lab
reports showing academic dishonesty.