0.1 Basic principles of genetics  (Page 8/19)

Lecture 7. the way from genes to traits

The following is an overview of the processes involved in turning the genes coded for in your DNA into the proteins that make up your body.  This is sometimes referred to as the "Central Dogma" of genetics.  

-Replication is the process by which DNA copies itself in order to be passed on to a new cell during cell division.

- Transcription is the process by which the DNA sequence of a gene is used to form an identical strand of mRNA which will be used to guide protein synthesis.

- Translation is the process by which the mRNA sequence is used to guide construction of a protein from its constituent amino acids.

Problems during any one of these processes can lead to a disruption of normal gene function, which can manifest itself as clinical disease.  How this can occur will be discussed in the following sections.

The genes in our DNA encode for the proteins that compose our body through the processes of transcription and translation, with messenger RNA being the intermediary.  

Transcription

The process of constructing mRNA from DNA is carried out by an enzyme, RNA polymerase , and is controlled through sequences in the genome termed promoters .  This process requires many different proteins and is tightly regulated to ensure proper gene expression.  Mutations in the proteins that are involved in replication, or mutations in the DNA promoter sequences themselves, can lead to improper expression and function of a gene.  A mutation in a promoter sequence that makes it non-functional would lead to decreased expression of the gene and, therefore, decreased amounts of a protein.  An example of this is a mutation in the promoter sequence for a component of hemoglobin, a mutation which leads to decreased amounts of functional hemoglobin.  This condition, ß-Thalassemia, leads to severe anemia and death by the mid-20's.  Transcription and the proteins regulating it are a vital part of gene function.

Transcription occurs in the cell nucleus.  Once the RNA is made, it is transported out of the nucleus to the cytoplasm, the location of translation.

Translation

Once formed, the modified proteins and their functions include the following:

-Enzymes, such as those in the digestive system.

-Structural components, such as the collagen in ligaments and tendons.