Station 4

Station 4: Who's the Daddy?

Background Information: 

Gel electrophoresis is a technique used in paternity testing to compare DNA from a child to potential fathers to establish paternity. 

One individual DNA molecule cannot be seen on a gel. However, all of the DNA molecules that are the same size will move the same distance through the gel. They will form a “band” of DNA that can be seen (Figure 4). The intensity or darkness of a band is due to the number of molecules of DNA that are running at that position on the gel. More DNA will cause the band to be darker. Less DNA will cause the band to be lighter.

In the case of paternity, the DNA of a child would exactly match the DNA of either of the two parents. In fact, you would expect that only about 50% of the bands in a child would match each parent (remember that meiosis generates haploid gametes that each contain 1 copy of each chromosome). However, all the bands in the child must come from one of the two parents: the child cannot have DNA that does not match with one parent or the other. Therefore, if any bands are not from the mother, they must be from the child’s father. Using this type of analysis, the paternity of an individual can be determined.

Use the image to determine which potential father is likely the child's biological father and answer on your handout.