This lesson will cover the process of transcription and its role in protein synthesis by looking at:
The path from genes to proteins involves two steps:
Transcription is the first step in protein synthesis. In transcription, a single strand of RNA is assembled using the DNA as a template. It pairs using the base pair rules except adenine will pair with uracil since RNA does not contain thymine. This process occurs in the nucleus of the cell. Certain proteins, called regulatory proteins, can stop or speed up transcription.
If RNA builds off of a DNA template, what makes RNA and DNA different?
Most importantly, both of these types of molecules contain genetic information, but the information RNA contains is specific to protein building.
There are three different types of RNA:
Ribosomes are composed of a large subunit and a small subunit. These subunits are made in the nucleolus and then sent out into the cytoplasm. Here they join together and help produce proteins during translation, the second step of protein synthesis.
Messenger RNA is the RNA that plays a role in transcription.
There are specific gene regions on a strand of DNA that code for certain types of proteins. RNA will combine with DNA in a process similar to DNA replication. RNA polymerase will unwind the DNA, and this will allow messenger RNA to form using the strand of DNA as a template.
RNA polymerases will just move down this gene region as that messenger RNA is built. When it's finished, the DNA will wind back up into what we started with up here.
Codons are sets of three nucleotides in messenger RNA that are used to build proteins; they code for amino acids. There are a total of 64 different codons that make up the genetic code and provide these protein making instructions.
Start codons mark the first amino acid of a polypeptide chain.
AUG is an example of a start code. This is adenine, uracil, guanine together in this chunk of three nucleotides. It would signal the start of a polypeptide chain.
A stop codon marks the end of a polypeptide chain. Stop codons are UAA, UAG, and UGA. It marks the end of a polypeptide chain, and that when that polypeptide chain would be finished being made.
In between, we have these other codons that code for specific amino acids. As those amino acids are being built, they are linked together and form polypeptide chains.
At this point, the mRNA is not completely finished. Introns are parts of the mRNA that don't code for proteins, and exons are the parts of the mRNA that do code for proteins. The introns get snipped out from the mRNA, and the exons are spliced together. After this, the mRNA can head into the cytoplasm for the next stage of protein synthesis, which is translation.
Transcription is the first step in the process of using genes to build proteins. DNA is used as a template for RNA to be built. There are three types of RNA : mRNA, tRNA, an rRNA. The RNA that plays a role in transcription is mRNA. Depending on the nucleotides that line up in this mRNA, it forms which then code for specific amino acids. The amino acids then form polypeptide chains. Once the nucleotides are joined, the mRNA is released from the DNA, and the DNA rewinds back together. Codons are sections of three nucleotides that code for amino acids. The start codon marks the first amino acid of a polypeptide chain, and the stop codon indicates the end of the chain.
Source: This work is adapted from Sophia Author Amanda Soderlind
Sections of 3 nucleotides that code for an amino acid.
Sections of RNA that code for proteins.
Information stored in the nucleotide sequence of DNA that forms our genes.
The formation of proteins by using information stored in DNA to form proteins.
An enzyme used to form a single strand of RNA from a DNA strand.
Proteins that can stop or speed up transcription.
A codon used to signal the start of an amino acid sequence on a strand of mRNA.
A codon used to signal the stop of an amino acid sequence on a strand of mRNA.
The process of converting DNA into RNA.
Messenger RNA that is used to convert RNA code into protein.
Ribosomal RNA is used to produce the structure of ribosomes.
Transfer RNA that is used to bind ribosomes to the start codon of a nucleotide chain in order for translation to occur.