DNA and Gel Electrophoresis

Vocabulary flashcards covering the molecular structure of DNA, biochemical principles of gel electrophoresis, lab procedures, and forensic analysis.

Gel Electrophoresis

A laboratory technique used to separate macromolecules such as DNA or RNA within a mixture based on their size, electrical charge, and shape.

Agarose

A polysaccharide substance derived from seaweed that forms a porous, uniform matrix through which molecules travel during electrophoresis.

TAE Buffer

A conductive salt solution mixed with agarose powder and used to completely submerge the gel in the electrophoresis rig to allow electrical current flow.

SYBR Safe

A fluorescent nucleic acid stain added to the molten agarose solution under a fume hood to allow visualization of DNA bands on a light box.

Gel Comb

A multi-pronged laboratory tool placed into the molten agarose in a gel bed to mold uniform wells for sample loading as the gel solidifies.

DNA (Deoxyribonucleic Acid)

A double-stranded, helical macromolecule packaged tightly in chromosomes within the nucleus that stores genetic instructions for living organisms.

Gene

A specific functional segment of DNA that codes for an organism's traits or proteins.

Nucleotide

The monomer building block of nucleic acids, composed of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base.

Anti-parallel

The structural arrangement of double-stranded DNA where the two complementary strands run in opposite directions alongside each other.

Base-Pair Rule

The pairing principle where adenine bonds with thymine via $2$ hydrogen bonds ($\text{A}=\text{T}$) and guanine bonds with cytosine via $3$ hydrogen bonds ($\text{G}\equiv\text{C}$).

Junk DNA (Intron)

Non-coding regions of the genome composed of repeating sequence patterns whose number of repeats varies between different individuals.

Restriction Enzyme

A molecular scissor protein that identifies and cuts DNA strands at specific recognition sequences to produce fragments for profiling.

Recognition Sequence

A specific sequence of nucleotide bases recognized, bound, and cleaved by a particular restriction enzyme.

Loading Dye

A substance mixed with DNA samples before gel loading that provides color for visualization and increases sample density so it sinks into the well.

STR (Short Tandem Repeat)

Short repeating patterns of non-coding DNA that vary in length among individuals; the FBI establishes $13$ STR loci for forensic DNA profiling.

Cathode

The negative electrode (black terminal) in an electrophoresis rig, positioned next to the sample wells so that negatively charged DNA runs away from it.

Anode

The positive electrode (red terminal) in an electrophoresis chamber toward which negatively charged DNA fragments migrate.

"Run to Red"

A laboratory mnemonic indicating that negatively charged DNA samples migrate away from the black (negative) cathode toward the red (positive) anode.

First Stop (Micropipette)

The primary point of resistance on a micropipette plunger, to which it should be depressed when loading a well to avoid expelling an air bubble that displaces the sample.

Biohazard Sharps Bin

The designated solid container used for the safe disposal of used micropipette tips during the lab activity.

Biohazard Soft Bin

The red, round disposal bin used specifically for discarding completed agarose gels.

Transcription

The cellular process in which RNA polymerase unwinds DNA and copies a nucleotide sequence into messenger RNA (mRNA), substituting uracil for thymine.

Translation

The process occurring at ribosomes in the cytoplasm where mRNA codons are read to synthesize specific proteins from chains of amino acids.

Codon

A three-letter nucleotide sequence on a strand of mRNA that codes for a specific amino acid building block of a protein.