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PCR and gel electrophoresis to determine genotypes

Today in the lab I was doing genotyping. Samples of DNA were collected from the latest litters of the lab’s colonies and their genotype had to be determined to check which of them carry genetic mutations in specific genes. Today’s experiments consisted of PCR (polymerase chain reaction) and agarose gel electrophoresis. This type of experiment is routine and is done almost every week in the lab. Today I genotyped 22 DNA samples. The process is relatively straight-forward and easy to perform. A detailed explanation of the exact method is described below.

Timelapse: Adding a purple loading dye to the samples to help assess how fast the DNA is running on the gel. It also contains a reagent to make the samples denser than the running buffer, so that the samples sink in the well.

Detailed methods of today’s experiment

Genotyping is a method used for determining differences in the genotype of an individual by comparing their DNA sequence for one particular gene to a reference sequence. Specific primers were designed that bind to and amplify the gene of interest in the genomic DNA of a sample. The amplified gene is then run on an agarose gel, a technique known as gel electrophoresis, to visualise the DNA and to help determine whether it is a wild-type or a mutant gene. An example of some of the genotyping results is shown below.

Some of the genotyping results showing the gene of interest, compared to known gene sequences and to a molecular-weight size marker (DNA ladder on the left and right ends).
Some of the genotyping results showing the gene of interest, compared to known gene sequences and to a molecular-weight size marker (DNA ladder on the left and right ends).