Study the DNA profiles obtained as a result of DNA fingerprinting of a child 'X' and three individuals 1, 2 and 3. Which one of the following options shows the possible parent of the child 'X' ?

The correct option is 1 and 3.

Concept and Principle of DNA Fingerprinting:
DNA fingerprinting (or DNA profiling) is a molecular technique used to determine genetic relationships. A child inherits half of their nuclear DNA from their biological mother and the other half from their biological father. Consequently, when analyzing DNA profiles on an electrophoresis gel, every single DNA band present in the child's profile (Child X) must align with a corresponding band in either the maternal or paternal DNA profile. If a band in the child's profile cannot be matched to either parent, those individuals cannot be the biological parents of the child.

Step-by-Step Analysis of the DNA Profiles:
By carefully examining the horizontal bands in the gel electrophoresis diagram for Child X, Individual 1, Individual 2, and Individual 3, we can match each of the child's bands to the potential parents:
1. Identify all the distinct horizontal band positions in the lane representing Child X from top to bottom.
2. Trace each band horizontally to see which of the three individuals (1, 2, or 3) shares a band at the exact same vertical position:
    • The upper bands of Child X align perfectly with the bands of Individual 1.
    • The remaining lower bands of Child X align perfectly with the bands of Individual 3.
    • Individual 2 has bands that do not match the positions required to account for the child's remaining bands when combined with the other individuals.
3. By combining the profiles of Individual 1 and Individual 3, we can account for 100% of the bands in Child X's DNA profile.

Therefore, Individual 1 and Individual 3 are the possible biological parents of Child X.