In this video, we're going to introduce short tandem repeats, which are commonly abbreviated as S. T. R. S. And so genetic markers used by researchers are generally made up of short repeat sequences that very end number. And so these are referred to as short tandem repeats, which again are commonly abbreviated as just S. T. R. S. And so these short tandem repeats, or STRS, are short repeated sequences of D N A that are approximately 2 to 5 nucleotides. Long NTS is an abbreviation for nucleotides, and they are found in very specific regions of the genome. Now the specific number of STRS, or short tandem repeats within this region of the genome is polymorphic, which means that it is going to be unique for each person in each individual and can be used to identify an individual. And so here, in this example, image down below. We're showing you just some examples of short tandem repeats. And so short tandem repeats, or SDRs are genetic markers that can be used to identify an individual, perhaps, uh, identifying the individuals by using D N A. That's found at a crime scene and so it can be helped it can be used to help solve a crime. And so if we take a look at this image down below, notice that the repeated sequence the short, uh, tandem repeat that we're looking at is this sequence right here where it is G a t A. Okay. And so this is the double stranded DNA and the short tandem repeat that were specifically focusing on in this image. And so what you'll notice is that we've got DNA from three different individuals down below individuals ones D N A is here. Then we have individual to, uh their d n A is there, and individual three's d N A. Is at the very bottom. And what you'll notice is that at this very specific region of interest in the chromosome, each of these three individuals differ and their number of short tandem repeats, or STRS And so what you'll notice is that individual number one has a total of five STRS five short tandem repeats, which would be unique to this specific individual number one individual number to notice it only has three of these short tandem repeats within this region of the genome, and that three would be unique to individual number two, An individual number three has a total of four short tandem repeats. And so the number of short tandem repeats is going to be unique for each individual. And it's going to be a genetic marker that can be used to again identify an individual and can be used to basically help solve a crime by comparing the DNA that might be found at the crime scene with the D N A. From the suspects. And so this year concludes our brief introduction to short tandem repeats or STRS, and we'll be able to get some practice applying these concepts as we move forward in our course, so I'll see you all in our next video.