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Bio Genetics DNA Lab 2 Questions

Bio Genetics: DNA


Tube Sample Lane

1 1 kb DNA ladder 1

2 Mother’s DNA 2

3 Child’s DNA 3

4 A.F. #1 DNA 4

5 A.F. #2 DNA 5

Record the distance each ladder band moved from the well in mm along with the size of the DNA fragments in that band in bp units, based on the bp given in step 19, in your Lab Notes.

Lane 1:

1,000 bp 34 mm

900 bp 36 mm

800 bp 38 mm

700 bp 40 mm

600 bp 43 mm

500 bp 47 mm

400 bp 51 mm

300 bp 56 mm

250 bp 60 mm

200 bp 64 mm

150 bp 69 mm

100 bp 77 mm

50 bp 90 mm


Lane 2:

37 mm 850bp

59 mm 265bp


Lane 3:

37 mm 850bp

44 mm 575bp


Lane 4:

41 mm 670bp

43 mm 600bp


Lane 5:

44 mm 575bp

55 mm 320bp

 Experiment: Agarose Gel Electrophoresis of DNA Fragments

Lab Results

  1. List the distances traveled in mm for the bands in the DNA ladder in the table below.
    Remember, smaller fragments travel farther than longer ones, so the top-most band will be the 1,000 bp-sized DNA fragments whereas the bottom-most band will be the 50 bp-sized DNA fragments.
DNA Ladder
Band Distance (mm)
50 bp  90 mm
100 bp  77 mm
150 bp  69 mm
200 bp  64 mm
250 bp  60 mm
300 bp  56 mm
400 bp  51 mm
500 bp  47 mm
600 bp 43 mm
700 bp 40 mm
800 bp 38 mm
900 bp 36 mm
1,000 bp 34 mm


2. Whose sample had the approximately 570 bp and 320 bp sized DNA fragments?

 A.F. #2

3. What were the sizes of the DNA fragments for alleged father #1?

 41 mm 670bp

43 mm 600bp

Data Analysis

4. Which size DNA fragment did the child inherit from her mother?

 37 mm 850bp

5. Which alleged father, if any, can be definitively ruled out as the child’s biological father?

 A.F. #2


6. How are new molecules of DNA synthesized in living cells?

7. What is the function of DNA?

DNA has genetic information that controls our cells. So, DNA is like a blueprint that shows how to construct components of cells like proteins and ribonucleic acid (RNA). This information is carried down to newer generations through inheritance.

8. If each individual has such a small amount of DNA in their cells, how do the bands on the gel contain enough DNA to be visible?

  In order to make DNA visible. The Gel has to be soaked in a dye (ethidium bromide) to bind with the DNA and rinsed off after. Ethidium bromide helps to make DNA visible by glowing brightly in UV rays.

9. Humans only have a few eye colors and only four ABO-based blood types. How can DNA tests definitively identify individuals when many people have brown eyes or type A blood?


10. Suppose a suspicious hair was found in a victim’s home. A gel is set up with the DNA fragments of two suspected criminals in lanes 4 and 5, the DNA fragments of the suspicious hair in lane 3, and the victim’s DNA fragments, as a negative control, are in lane 2. A DNA ladder is in lane 1. The resulting gel is below. Which suspect, if any, committed the crime? Explain your answer.


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