How DNA Directly Affects You

Protein synthesis is a very complicated process. Protein synthesis has many steps, and a variety of chemicals and organelles are involved. Deoxyribonucleic acid (DNA) is the controlling force behind protein synthesis, but DNA alone cannot form proteins.

Transcription is the first step in the long process of protein synthesis, and takes place in the nucleus of the cell. Transcription is the process of DNA transcribing ribonucleic acid (RNA). Transcription is slightly similar to DNA replication, as in the beginning, the DNA unzips. However, instead of the DNA replicating into two molecules of DNA, a new kind of molecule forms, which is RNA. RNA is like DNA, except it has oxygen in it (deoxy means without oxygen, so when deoxy is removed, oxygen is added). Also, the nitrogen base uracil replaces all instances of the nitrogen base thiamine.

During transcription, only parts of the DNA molecule transcribe. These parts are called genes, and each gene codes for a certain protein. Here is what a gene looks like when it transcribes into RNA. If the gene's nucleotide sequence is:

AATGCGGT

Then the nucleotide sequence of the RNA molecule will be:

UUACGCCA

The next step of protein synthesis is translation, which is the RNA coding for amino acids. First, there are some more things that are to be known about RNA. First, three nucleotides in an RNA molecule are called a codon, and each codon codes for a certain amino acid. A string of RNA with codons that code for amino acids is called messenger RNA. The messenger RNA leaves the nucleus and enters the cytoplasm. There, it meets up with another type of RNA, called transfer RNA. Transfer RNA has a part called an anticodon, which is complementary to an RNA codon. Transfer RNA with a certain anticodon is set to carry a certain amino acid. Transfer RNA attaches to the messenger RNA, via base pairing rules, and once the transfer RNA attaches, more transfer RNA come and attach and incorporate their amino acid into the growing polypeptide chain.

Where does the protein sequence start? It starts with a start codon, which is the codon sequence AUG. Likewise, there is a stop codon, which stops, or ends, the polypeptide chain. A stop codon can be one of three nucleotide sequences: UAA, UAG, or UGA. Once a stop codon comes up, the protein is complete, and it is released freely into the cytoplasm.

There is another factor in protein production, an important one. That is the ribosome, which is where translation takes place, on the ribosome. Some of the ribosome itself is composed of an RNA called ribosomal RNA, but since it is long lasting, it is not transcribed often.

This is a simplified explanation of protein synthesis. There are many kinds of enzymes involved, and other little "mini processes" which contribute to the entire process of protein synthesis. However, this is a quite detailed general overview of protein synthesis.