Name____________________________
Date ________ Period_____ Group____
DNA Typing Results
Differences in DNA can be examined to show unique differences in length among individuals.
For each person in our simulation, the DNA sample represents pieces of DNA cut from the
same locus (place) on each of two chromosomes (a homologous pair). These DNA pieces may
be the same length or different lengths. Gel electrophoresis was used to separate the DNA
pieces according to their length. After running the gel, DNA pieces of the same length collected
together at one spot on the gel. After straining the DNA, you could see comparative lengths of
DNA from each person. Remember, shorter fragments moved farther through the gel than did
longer fragments. Each allele is represented by a band made of many copies of a DNA fragment
of a certain length.
If a person is HOMOZYGOUS (same allele on each member of a chromosome pair) for a
certain trait, all of their DNA fragments will be the same length and will therefore move the same
distance and create just one band.
If a person is HETEROZYGOUS (different alleles on each member of a chromosome pair) for a
certain trait, they will have two different length DNA fragments which will move different
distances and create two bands.
Did you use DNA from case 1 or case 2?
M+
B+
S+
Draw in the
results from
your gel.
Circle your answer. Was the:
Suspect: homozygous or heterozygous?
Baby: homozygous or heterozygous?
Mother: homozygous or heterozygous?
M+
B+
S+
Draw the ideal sample.
Suspect: homozygous or heterozygous?
Baby: homozygous or heterozygous?
Mother: homozygous or heterozygous?
Should the suspect be included or excluded?
Explain in what ways (if any) your data differs from the best data for your case:
If your data differs, what sources of error could have contributed to you results?
Draw the ideal for the case you didn’t have:
Is it case 1 or 2?
Was the:
Suspect: homozygous or heterozygous?
Baby: homozygous or heterozygous?
Mother: homozygous or heterozygous?
Would the suspect be included or excluded?
DNA Fingerprinting Discussion
1. Why are there two lanes devoted to each person’s DNA (one for uncut, and one for cut
DNA)?
2. The Hind III restriction enzyme was used in this lab.
a. What is the function of Hind III (restriction enzyme)?
b. What specific DNA sequence does the restriction enzyme cut (show sequence and
location of cut).
c. Why was the same restriction enzyme used on all DNA samples?
3. Explain why the uncut version showed multiple bands.
4. What is the relationship between the distance the DNA migrates and its size?
5. Why is the DNA placed at the cathode (negative) end of the gel box?
6. Which case did your DNA come from (1 or 2)?
7. Using your DNA gel photo (comparing only the cut DNA bands), determine if the baby (B)
could belong to the mother (M). Explain.
8. Using your DNA gel photo (comparing only the cut DNA bands), determine if the baby (B)
could belong to the suspected father (S). Explain.
9. Using your DNA gel photo (comparing only the cut DNA bands indicate if the suspect
must be, could be or could not be the father of the baby based only on the data we have
so far. Why?