4D- gel electrophoresis Flashcards
(14 cards)
What is gel electrophoresis?
A technique that separates DNA fragments based on their molecular size.
What is a well in gel electrophoresis?
An indent in the gel into which a DNA sample is loaded.
What is a standard ladder?
A mixture of DNA fragments of known length that are used to infer the size of fragments in a sample.
What is agarose gel?
A sponge-like gel used in gel electrophoresis that contains pores for DNA fragments to move through.
What is a buffer in gel electrophoresis?
An ion-rich solution that carries electrical current through the agarose gel.
What is an electrode?
Conductors of electricity that are attached to both ends of a gel allowing an electrical current to pass through it.
What is a band in gel electrophoresis?
A line seen in the gel after running gel electrophoresis that corresponds to a collection of DNA fragments of a specific size.
What is ethidium bromide?
A fluorescent dye that binds to DNA fragments in a gel and allows them to be easily visualised under ultraviolet light.
What is genetic testing?
Screening an individual’s DNA for anomalies that may make them susceptible to a particular disease or disorder.
What is DNA profiling?
The process of identification on the basis of an individual’s genetic information.
What does homozygous mean?
Having identical alleles for the same gene on homologous chromosomes.
What does heterozygous mean?
Having different alleles for the same gene on homologous chromosomes.
What are short tandem repeats (STR)?
Short, repeated sequences of nucleotides found in the non-coding regions of nuclear DNA. cuz hey are found in non-coding regions- not affected by natural selection- many hundreds of variant STRs
process of gel electrophoresis
The DNA samples are placed in the wells at one end of the gel using a micropipette. A standard ladder of DNA fragments with known sizes is also typically loaded into one well. required for estimating the size of any unknown DNA fragments by comparing them to known fragments in standard ladder.
The gel = agarose, a sponge-like jelly that is filled with tiny pores to allow movement of DNA fragments. agarose gel is immersed in a buffer solution helps carry an electric current.
An electric current is passed through the gel using two electrodes – one positive, one negative. negative electrode= positioned near the wells and the positive electrode= the opposite end of the gel. - DNA is negatively charged due to the phosphate backbone, attracted to positive electrode. When the electrical current applied- DNA fragments move from the wells, through the tiny pores in agarose gel, towards positive electrode.
Smaller DNA fragments move faster through the gel and travel further than larger fragments- which don’t move as easily through the pores in the agarose.
After a few hours, the current is switched off and, the DNA fragments stop moving in the gel and settle into bands. The DNA fragments are now separated based on size.
DNA is difficult to see with the naked eye so the gel is stained with fluorescent dye e.g ethidium bromide, allow the bands of DNA to be visualised under an ultraviolet (UV) lamp. dye included in the gel before or after the experiment.
