DNA bases

There are 4 different bases in the DNA. These include the bases derived from pyrimidine with only one ring (cytosine and thymine) and the bases derived from purine with two rings (adenine and guanine). These bases are each linked to a sugar and a phosphate molecule and are then also called adenine nucleotide or cytosine nucleotide.

This coupling to the sugar and to the phosphate is necessary so that the individual bases can be linked to form a long DNA strand. In the DNA strand, sugar and phosphate alternate, forming the lateral elements of the DNA ladder. The ladder steps of the DNA are formed by the four different bases, which point inwards.

Adenine and thymine, or guanine and cytosine always form a so-called complementary base pairing. The DNA bases are linked by so-called hydrogen bonds. The adenine-thymine pair has two, the guanine-cytosine pair three of these bonds.

DNA Polymerase

DNA polymerase is an enzyme that can bind nucleotides together to produce a new DNA strand. However, the DNA polymerase can only work if a so-called “primer”, i.e. a starting molecule for the actual DNA polymerase, has been produced by another enzyme (another DNA polymerase). The DNA polymerase then attaches to the free end of a sugar molecule within a nucleotide and links this sugar to the phosphate of the next nucleotide.In the context of DNA replication (amplification of DNA in the process of cell division), the DNA polymerase produces new DNA molecules by reading off the already existing DNA strand and synthesizing the corresponding opposing daughter strand. In order for the DNA polymerase to reach the “parent strand”, the actually double-stranded DNA must be wrested from the parent strand by preparatory enzymes during DNA replication. In addition to the DNA polymerases that are involved in the amplification of DNA, there are also DNA polymerases that can repair broken spots or incorrectly copied spots.

DNA as material and its products

In order to ensure the growth and development of our body, the inheritance of our genes and the production of the cells and proteins necessary for this, cell division (meiosis, mitosis) must take place. The processes our DNA has to go through for this are shown in the overview: Replication: The goal of replication is the duplication of our genetic material (DNA) in the cell nucleus, before cell division. The chromosomes are removed piece by piece so that enzymes can attach themselves to the DNA.

The opposing DNA double strand is opened so that the two bases are no longer connected. Each side of the handrail or base is now read by different enzymes and supplemented by the complementary base including the handrail. Thus two identical DNA double strands are formed, which are distributed to the two daughter cells.

Transcription: Just like replication, transcription takes place in the cell nucleus. The aim is to transcribe the base code of the DNA into an mRNA (messenger ribonucleic acid). In the process, thymine is exchanged for uracil and DNA parts that do not code for proteins are cut out, similar to a blank.

As a result, the mRNA, which is now transported out of the cell nucleus, is much shorter than the DNA and is only single-stranded. Translation: Once the mRNA has reached the cell space, the key is read from bases. This process takes place on ribosomes.

Three bases (base triplet) give the code for an amino acid. Altogether 20 different amino acids are used. When the mRNA has been read off, the strand of amino acids results in a protein which is either used in the cell itself or sent to the target organ.

mutations: During propagation and reading of the DNA, more or less serious errors can occur. In a cell, there are about 10,000 to 1,000,000 damages per day, which can usually be repaired by repair enzymes, so the errors have no effect on the cell. If the product, i.e. the protein, is unchanged despite mutation, then a silent mutation is present.

If the protein is changed, however, disease often develops. For example, UV radiation (sunlight) causes damage to a thymine base to be irreparable. The consequence can be skin cancer.

However, mutations do not necessarily have to be associated with a disease. They can also change the organism to its advantage. Thus, mutations are a major component of evolution, because organisms can only adapt to their environment in the long term through mutations.

There are various types of mutations that can occur spontaneously during different cell cycle phases. For example, if a gene is defective, this is called a gene mutation. However, if the defect affects certain chromosomes or parts of chromosomes, then it is called a chromosomal mutation. If the number of chromosomes is affected, it then leads to a gene mutation.