Procedure I – DNA Fragment Size
In the table below indicate which sample contains the smallest DNA fragment and which sample contains the largest DNA fragment. Note: Sample 1 is in Lane 1 of the gel, etc.
Lane
1
Fragment
Lane
2
Fragment
Lane
3
Fragment
Lane
4
Fragment
Lane
5
Fragment
Observations and Questions
[1] [a] What is the composition of DNA? [b] How are DNA fragments created?
Answers:
[a]
[b]
[2] Using the lane numbers on the electrophoresis instrument, list the samples from smallest DNA fragment to largest DNA fragment.
Answer:
Smallest ______ ______ ______ ______ ______ Largest
[3] [a] How does gel electrophoresis cause DNA to move downward on the gel?
[b] What accounts for the different final locations of the different size DNA fragments? That is, why do different sized DNA fragments end at different locations on the electrophoresis instrument?
Answers:
[a]
[b]
Procedure II – Crime Scene DNA
In the table below indicate the number of DNA fragments each sample has in common with the crime scene sample (Lane 2). Note: Sample 1 is in Lane 1 of the gel, etc.
Tip: It is helpful to use a ruler when attempting to match up DNA fragments in the gel. A bank/ATM/credit card works well too.
Lane
1
Student
Lane
2
Crime Scene
Lane
3
Suspect
Lane
4
Suspect
Lane
5
Suspect
6
Observations and Questions
[4] Does the crime scene sample contain bands in common with the student? Explain why or why not.
Answer:
[5] Which suspect (if any) CANNOT be excluded from suspicion? Explain your answer.
Answer:
Procedure III – Paternity Case
In the table below indicate the number of DNA fragments each sample has in common with the child/calf sample (Lane 2). Note: Sample 1 is in Lane 1 of the gel, etc.
Tip: It is helpful to use a ruler when attempting to match up DNA fragments in the gel. A bank/ATM/credit card works well too.
Lane
1
Mother
Lane
2
Calf
Lane
3
Male
Lane
4
Male
Lane
5
Male
6
Observations and Questions
[6] Which sample is from the father of the calf? Explain your answer.
Answer:
[7] How many bands does the calf have in common with its mother? How many bands does the calf have in common with its father? Propose a plausible explanation for the number of bands from each parent.
Answer:
[8] After adding the probe and filter, what additional information have you learned about the genotype of the calf?
Answer:
[9] Given that the probe pairs with a specific DNA strand in the matrix, what can you conclude about the nucleotide sequence of the Baby’s DNA fragment that pairs with the probe sequence?
Answer:
[10] Discuss reasons that it might be useful to find out whether a newborn carries a specific gene or allele.
Answer:
Procedure IV – Species DNA Comparison
Observations and Questions
[11] In your own words, explain why it is necessary to include only one chain-terminating/synthesis-terminating nucleotide in each well of the electrophoresis instrument.
Answer:
[12] Determine the DNA sequence by analyzing the location of each nucleotide across the four lanes of the electrophoresis instrument. Provide the DNA sequence as your answer here.
Important: remember that your sequence starts from the shortest fragment!
Answer:
[13] What is the significance of finding that DNA sequences are highly similar for two different species?
Answer:
[14] Below, align the newly determined DNA sequence for the unknown species with the sequences of the three known plant species (see data under the Activity Form tab). Next, compute the percent alignment of the bases for the three comparisons.
Show the alignment and percent alignment calculation for Plant 1. Highlight the Plant 1 differences in yellow.
Plant 1: TCAGCGTGACTAACTG (data from the Activity Form tab)
Unknown:
Calculation (% similarity):
Show the alignment and percent alignment calculation for Plant 2. Highlight the Plant 2 differences in yellow.
Plant 2: TCATCGTCGCTAACGT (data from the Activity Form tab)
Unknown:
Calculation (% similarity):
Show the alignment and percent alignment calculation for Plant 3. Highlight the Plant 3 differences in yellow.
Plant 3: TGATCGACGCTAACGA (data from the Activity Form tab)
Unknown:
Calculation (% similarity):
Which known species has a genotype that is most similar to that of the unknown plant?
Answer:
[15] A biologist at World University used Procedure IV to conduct an additional study and found the sequence following below. Using your knowledge of central dogma generate the amino acid (AA) sequence that results from this sequence.
Given DNA sequence: CAC GAC GGA TTC GTA
Answer:
– DNA sequence: CAC GAC GGA TTC GTA
– mRNA sequence:
– AA Sequence:
