What does DNA do

DNA

DNA / DNA basics

DNA or DNA basics is the first topic in the superordinate chapter Genetics. We'll show you how DNA is built and what parts it consists of. To do this, we explicitly look at the structure of nucleotides and how a DNA strand is created from them.

DNA topics on this page

Before we dive right into the topic of DNA, we should first clear up the confusion behind the acronyms DNA and DNA. Here is a precise word description:

English: DNA (D.eoxyriboNucleic A.cid)

German: DNS (D.esoxyriboneNucleinS.acid)

The terms DNA and DNA differ only in their origin, not in their meaning. DNA is simply the English version of the term DNS. The term DNA is more common, which is why we will use it in this article. Now we come to the main topic of this article: The structure of DNA.

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How is the DNA (German "deoxyribonucleic acid") structured?

The DNA is made of so-called Nucleotides built up. Remember this term as it will be important for building a strand of DNA.

Each Nucleotide again consists of 3 parts:

  • a phosphate group (P),
  • the sugar deoxyribose
  • and one of four organic bases (adenine, thymine, guanine and cytosine).

Let's first look at a simplified representation of a nucleotide before we go into detail:

If you take a closer look at the diagram, you will see that the term Pentose falls here the first time. Before we get confused, let's start with this building block of DNA.

The pentose


A pentose is a sugar with five carbon atoms. These are arranged from 1 to 5 clockwise (see symbol graphic). What you have to remember in any case is the following: Deoxyribose is part of the structure of DNA, whereas ribose is part of the structure of RNA. (Here to the RNA article)

As you can see from the pictures, the difference between deoxyribose and ribose lies in the missing oxygen atom (O-atom). This knowledge is important later in order to be able to understand the chaining of nucleotides to a DNA strand. But more on that later.

In order to be able to form the so-called "DNA backbone" (pentose + phosphate group), we must first look at the phosphate groups. This is the P in the graph of the nucleotide sketched above.

What are phosphate groups (also called phosphate residues)?

In the DNA, the phosphate group always docks to the 5th carbon atom of deoxyribose. That is also the reason why the P is coupled to the 5 above in the sketch of the nucleotide. We'll find out later why the important number 3 appears there and can be left out when looking at a single nucleotide.

The DNA backbone therefore consists of the pentose and the phosphate group. Why the combination of the two components is so-called can best be explained graphically:

As you can see from the graphics, the DNA backbone, i.e. the phosphate group and deoxyribose, form the strands of the "DNA ladder". We'll take a closer look at what the rungs between the strands are in the next section.

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Bases overview

After looking at the phosphate groups and deoxyribose, the third part of a nucleotide is still missing: the base.

As you can see in the sketch above, the base combines in a nucleotide at the 1st carbon atom of deoxyribose. The important thing is that there are four organic bases that look like this:

Above we wrote that there are 4 organic bases, but why are we listing 5 here? The answer is this: There are two basic bodies for organic bases. your name is Pyrimidine bases and Purine bases.

Purine bases: (adenine, guanine)

Pyrimidine bases: (cytosine, thymine, uracil)

So we see that there are 5 bases based on two different primitives. What is important to know is that Adenine, Guanine, Cytosine and Thymine occur in the DNA, whereby the base thymine is exchanged for the base uracil in the RNA, so that there Adenine, Guanine, Cytosine and Uracil occurrence.

Task of the base in the DNA?

Two nucleotides connect with each other via the bases, one of the two purine bases always connecting with one of the two pyrimidine bases. In the graphic, two connected nucleotides look like the one on the left.

And how is a DNA strand formed?
By linking several nucleotides.

As can be seen in the picture, the C3 atom (3 ‘) of the upper pentose connects with the phosphate group of the lower nucleotide.
The two strands of the helix run in opposite directions, i.e. antiparallel: the 5 Dem end of one strand is antiparallel to the 3‘ end of the complementary strand. These ends correspond to the respective carbon atoms of the ribose.


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