Central Dogma of Molecular Biology

 CENTRAL DOGMA OF MOLECULAR BIOLOGY

Gene expression is the process through which organisms transform information in the nucleic acids into proteins. It takes place thanks to a series of complex mechanisms that are very similar in all livng thing.

According to this, we can define a gene as a segment of DNA that contains the essential information to synthesise a protein.

Central dogma of molecular biolgy

Francis Crick poposed the central dogma o molecular biology in 1958, which states;

Each time a cell divides, DNA duplicates itself throungh replication. When a protein is needed, the DNA gene that codifies that particular protein in trascribed into RNA that leaves the nucleus and goes into the cytoplam. Then the gene is translated and the protein is synthesised.

Crick´s proposal had a range of critics and was revised in 1970. Nowadays, it has been modified because of the following reasons:

• The term dorgma refers to a belief that cannot be questioned. This concept is incompatible with science and the sciencific method. Crick himself recognised that it was a mistake to use that term.

• A second modification was made after the Discovery of certain viruses, such a AIDS, that have RNA as genetic material. These viruses aynthesise their DNA from their RNA, using a process called inverse transciption.

• Anothe modification was made after prions were discovered. Prions are proteins capable of propagating without the help os DNA.

• The last modification was made alter ribozymes were discoverd. Ribozymes are RNA molecules that can self-replicate.

After the modification, Crick´s proposal has been expressed as the following hypothesis:

The route followed by most living things in shown in blue, whilst special cases are in pink.

Transcription

DNA found in eukaryotic cells copies part of its genetic information into another molecule: RNA (ribonucleica cid).

Transcription is the process through whic part of the genetic information in copied from original form (DNA) intro mRNA.

Transcription takes in the nucleus of the cell. mRNA is then released into the cytoplasm through the pores of the nuclear membrane.

The mRNA released is complementary to the tragment of DNA that hs been transcribed, which is the sequence that codifies a particular that the cell may need. This is why, duning this process. Accuracy is esential and the sequence of ribonucleotides must be perfect.

Translation

Is the process though which proteins are synthesised by using the information contained in the

mRNA molecule formed during transcription.

Translation takes place inside the ribosomes.

It is essential that no mistakes are made when amino acids are incorporated into the growing protein. This is because each type of protein is characterised by the amino acis sequence it carries, as it provides the protein with its particular function.

In order for translation to happen, the following elements are neede:

• An mRNA molecule created from the transcription of a DNA fragment.

• Ribosomes, which are organelles capable of Reading the mRNA molecule. They can be moving freely in the cytoplasm or joined to the endoplasmic reticulum.

• Trnasfer RNA (tRNA), which are RNA molecules that carry amino acids to the ribosomes. A particular type of tRNA transport each type of amino acid.

• Free amino acids in the cytoplasm.

Translation begins when a cell needs a particular protein. In order to speed up the synthesis, the process takes place in different parts of the mRNA molecule.