DNA & Gel Electrophoresis: Key Concepts for Forensics and Genetics

buccal swab

A cheek swab used to collect DNA from mouth cells.

DNA fingerprinting (profiling)

A process that compares DNA band patterns to identify people.

gel electrophoresis

To separate DNA fragments by size using electricity.

DNA movement in gel electrophoresis

DNA is negatively charged, so it moves toward the positive end.

DNA movement direction in gel

From the negative (black) electrode to the positive (red) electrode.

small DNA fragments movement

They fit more easily through the agarose gel pores.

agarose

A jelly-like substance from seaweed used to make the gel.

buffer in gel electrophoresis

It conducts electricity and keeps the pH stable so DNA moves correctly.

DNA ladder

To compare and estimate the sizes of DNA fragments (like a ruler).

CODIS

Combined DNA Index System — the U.S. FBI DNA database.

STRs (Short Tandem Repeats)

Repeating DNA sequences used to identify people.

STRs for gender testing

Y-STRs are found on the Y chromosome, identifying male DNA.

primers

Short DNA pieces that tell enzymes where to start copying DNA during PCR.

power supply in gel electrophoresis

It provides the electric current that moves DNA through the gel.

bands in a gel

Groups of DNA fragments of the same size.

different band positions

Smaller fragments travel farther; larger ones move less.

common uses of DNA fingerprinting

Forensics, paternity testing, identifying remains, genetic studies.

charge of DNA

Negative.

DNA sample loading into wells

The wells hold DNA in place before the current separates it by size.