The DNA located within the nucleus exists as a double-stranded molecule. Many regions of this DNA contain transient gene contents, while others regulate gene expression.
In regions containing genetic information or genes, one strand is a coding strand and the other is a non-coding strand.
The coding strand carries the code and is not copied from the non-coding template strand.
This non-coding strand actually serves as the template, providing the information to be extracted.
DNA Template and Transcription
The DNA you currently possess actually originates from genetic information.
This information encodes instructions for all cellular functions. For your cells to function properly, this information must be transferred from the DNA residence to the cytoplasm.
As DNA cannot leave the nucleus, you first need to make a copy. This process is also known as gene expression.
The initial step in gene expression is transcription.
In the process of DNA, it will be transcribed into RNA by the RNA polymerase enzyme.
The resulting RNA can be stored and used as a product of RNA genes, such as ribosomal RNA. This can serve as a template for protein production, often referred to as RNA.
Above is a comprehensive overview of transcription. Now, let’s delve deeper.
When the DNA sequence is read by RNA polymerase, a complementary and antiparallel RNA strand is produced. What is meant by complementary and antiparallel?
The nucleotide sequence in the template strand complements the template strand. However, they run in opposite directions, like antiparallel.
The copy of the template strand read by the ribosome then produces a protein through translation. Why use the non-coding strand as the template?
When you mention the coding strand, why don’t we use it as the code for gene products?
In essence, what we desire is a protein that acts as a complementary copy to the parallel DNA strand we possess. As a result, the copy of the DNA template is used because it is the version that complements but is antiparallel to the coding gene itself.
This generates an RNA that complements the DNA and aligns with the presence of the gene.
DNA Template and PCR
Do you know what PCR is? PCR stands for Polymerase Chain Reaction.
PCR is a technique within molecular biology. It is commonly used to amplify DNA sequences.
It is an immensely powerful tool that can create multiple copies of a gene sequence, ranging from thousands to millions. This technique gained fame during the O.J. Simpson trial.
Forensic scientists also employ it to amplify DNA found in blood samples at crime scenes.
The method relies heavily on repeated cycles of heating and cooling, as well as the mixing of chemical components.
The mixture includes DNA, nucleotides, enzymes, and primers, all in much smaller volumes. Starter DNA and all the DNA generated in the PCR process are used as templates.
The rationale behind thermocycling is that each step in the PCR process involves different temperatures. This ranges from separating the double-stranded DNA to raising and lowering the temperature.
