The genome is comprised of chromosomes which contain DNA, the molecule essential for producing proteins and thus, expressing genes. In order to read the genome and express genes, DNA must create RNA which then is utilized to synthesize proteins.
Protein production requires two important processes, these are transcription and translation. In a nutshell, transcription is a process in which the DNA double helix becomes unwound and gets translated into mRNA within the cell nucleus. This mRNA then undergoes splicing and receives a 5’ cap and a 3’ tail so that it is able to leave the nucleus and safely enter the cytoplasm so that this mRNA can be read. Splicing is necessary so that only the appropriate DNA is encoded and the 5’ cap and 3’ tail are needed to protect the mRNA which must travel in the cytoplasm.
The process of translation is required to actually synthesize the protein. Translation is done using ribosomes found in the cytoplasm. These ribosomes read the mRNA and attach the complementary tRNA molecules which carry the appropriate amino acids. A series of amino acids joined together make up a polypeptide and proteins are composed of polypeptides.
It is through gene expression and the controls inflicted upon gene expression that the cells within an organism become differentiated, creating the different phenotypes which exist. Genes are controlled through different methods such as developmental programs and variations in promoter sequences for instance.
Furthermore, in terms of gene expression, certain processes such as post-transcriptional processes and post-translational modification alter the function of particular proteins. Other factors, for example, the fact that some genes are only expressed in certain tissues, also greatly influence gene expression and organism differentiation.
Evidently, the genome and gene expression are two incredibly related concepts. Understanding these concepts is instrumental to the study of genetics and analyzing the uniqueness of all species which exist.