Video Transcript
The paternity of a child is in
dispute. A DNA fingerprint was constructed
for the child and their mother. DNA fingerprints from samples taken
from four possible fathers are constructed. Based on the information in the
diagram provided, state which male is most likely to be the child’s father.
This question ask us to determine
which male is the father of the child through the process of DNA fingerprinting. Just like how your fingerprint is
different from every other person’s in the world, your DNA fingerprint is incredibly
unique. The process of DNA fingerprinting
actually creates a visual profile of a person’s unique DNA sequence through gel
electrophoresis.
Gel electrophoresis is a process
that first breaks up long strands of DNA into shorter fragments through special
proteins called restriction enzymes. Since every person has a slightly
different sequence of DNA, these fragment lengths will differ between
individuals. These fragments are then run
through a gel that contains an electric current. The electric current causes DNA to
move towards the positive end because DNA has a negative charge. Because the fragments are moving
through a thick gel, the smaller fragments will move further than the larger
fragments. This creates a unique pattern of
fragments for each individual, a DNA fingerprint.
In the image provided of DNA
fingerprints, the shaded regions represent the DNA fragments for each
individual. Notice that each person’s fragment
pattern is different. You may have learned that children
get half of their genetic information from each parent’s gamete during
fertilization. This concept is how DNA
fingerprints are used to determine paternity. All of the child’s fragments of DNA
were inherited from either the child’s mother or father. Let’s highlight the shaded bands
which represent the fragments of DNA from the child. We can compare the child’s DNA to
the mother’s DNA and find the fragment patterns that match. We can then eliminate all the DNA
fragment patterns from the child that matches the mother’s because this DNA was
inherited from the mother.
We are looking for the DNA
inherited from the father to determine paternity. The remaining fragment patterns of
DNA could not have been inherited from the mother. Therefore, they had to have been
inherited from the biological father. So we examine each of the potential
fathers for which male has the matching fragment patterns of DNA for those
segments. Can you spot which father has
matching DNA fragment patterns to the ones highlighted in the child’s DNA
fingerprint? As you can see, male 3 shares the
same DNA fragment patterns as the child. Therefore, the male that is most
likely to be the child’s father is male 3.
