Final answer:
Molecules can move through gels because the gel acts as a molecular sieve in the process of gel electrophoresis, separating DNA molecules by size based on their rate of migration through the gel matrix.
Step-by-step explanation:
Understanding Gel Electrophoresis and Molecular Movement
Molecules can move through gels – a concept utilized in the technique known as gel electrophoresis. This method is used for separation by size, specifically in the analysis of DNA fragments. Gel electrophoresis exploits the property that nucleic acids are negatively charged under certain pH conditions, allowing them to respond to an electric field. The porous structure of the gel acts as a molecular sieve, separating DNA molecules based on size. Larger DNA fragments move slowly through the gel because they experience more friction within the smaller pores, while smaller DNA fragments move more rapidly due to lesser friction. Visualized using Figure 14.9 and Figure 17.3, gel electrophoresis can separate DNA fragments, making it possible to differentiate between them based on the distance they travel within the gel. Essentially, the rate at which molecules migrate in gel electrophoresis is governed by the equation v = q E/f, where v is the velocity (rate) of migration, q is the charge on the molecule, E is the electric field's strength, and f is the friction opposing the movement. Consequently, DNA with higher molecular weight or more elongated shapes travels a shorter distance than compact or lower molecular weight DNA. This method is crucial in various biological and medical research applications, such as genomic studies and disease diagnosis.