Question Video: Recalling the Characteristic of DNA That DNA Fingerprinting Uses Biology

Some characteristics of eukaryotic DNA are provided in the list below. 1. Eukaryotic DNA is contained within the nucleus. 2. Eukaryotic DNA is linear. 3. The majority of eukaryotic DNA is noncoding and varies between individuals. 4. Eukaryotic DNA is bound to histone proteins. Which characteristic does DNA fingerprinting rely on?

03:24

Video Transcript

Some characteristics of eukaryotic DNA are provided in the list below. (1) Eukaryotic DNA is contained within the nucleus. (2) Eukaryotic DNA is linear. (3) The majority of eukaryotic DNA is noncoding and varies between individuals. (4) Eukaryotic DNA is bound to histone proteins. Which characteristic does DNA fingerprinting rely on?

This question is asking us about DNA fingerprinting, which has many important applications. It is a technology that takes advantage of the unique sequence of nucleotides present within the cells of each individual. As eukaryotes, our DNA is contained in the nucleus of our cells. We have a lot of DNA. In fact, if you were to take out all the DNA from a single cell and stretch it out, it would be about two meters in length. This isn’t one long, continuous molecule of DNA. Instead, it’s organized into structures called chromosomes. In humans, we have 23 pairs or 46 chromosomes in total. Let’s take a closer look at one of these chromosomes.

DNA is wound up tightly around special proteins called histones. And this is how so much DNA can be packed into the nucleus of one of our cells. Our DNA is made up of repeating subunits called nucleotides, each of which contains a nitrogenous base that can be either guanine, or G for short, cytosine, adenine, or thymine. Let’s represent the total DNA, or the genome, of two individuals as these two lines. We have over three billion nucleotides in our genome, with the majority of it being noncoding DNA, which is DNA that doesn’t code for proteins. Between humans, our DNA is very similar, and about 99.9 percent of it is the same. But there are some differences, and we’ll indicate them as black dots in the DNA of person B.

Here you can see one nucleotide that’s different. In person A, at this position is an adenine, while in person B it’s a cytosine. In order to see these differences, we can use special enzymes, called the restriction enzymes, that can cut DNA at specific nucleotide sequences. Let’s say that this restriction enzyme only cuts the DNA sequence GAATTC. The DNA in person A has this sequence at this particular site, so it will be cut by the restriction enzyme. However, person B has a different nucleotide at this position, so the restriction enzyme won’t cut their DNA at that point.

Because of these differences between these two sequences, this results in a different number of cuts throughout the DNA of person A and person B. These cuts produce different fragments of DNA that are different sizes. Using a special technique called gel electrophoresis, these fragments can be arranged by their size in a gel and photographed. This pattern of fragments that we see in the gel is unique to each individual and is why we call this a DNA fingerprint.

Now that we understand how a DNA fingerprint is made from the unique differences in the nucleotide sequence between individuals, we can answer our question. The number that corresponds to the characteristic that DNA fingerprinting relies on is number (3). The majority of eukaryotic DNA is noncoding and varies between individuals.

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.