Start and stop codons are important because they tell the cell machinery where to begin and end translation, the process of making a protein. The start codon also sets up the reading frame of the DNA strand, indicating that each triplet after that point codes for a specific amino acid.Continue Reading
Start and stop codons are found both on the original DNA strand in the nucleus of the cell and on the messenger RNA strand that serves as the protein template. The mRNA that corresponds to a specific gene on the DNA strand is synthesized in the nucleus using the antisense strand of DNA as a guide to the order of codons. This mRNA strand then travels to a ribosome in the cell nucleus, where protein assembly takes place.
In most organisms, the only start codon is ATG, a triplet made up of the DNA bases adenine, guanine and thymine. ATG also codes for the amino acid methionine when found in the middle of a gene. In the mRNA template, ATG is replaced by AUG because the base uracil always appears in place of thymine in RNA.
Stop codons come in three different forms: TGA, TAG and TAA. In RNA, these three codons appear as UGA, UAG and UAA. Unlike the start codon, none of the stop codons code for an amino acid.Learn more about Molecular Biology & DNA
A codon is a set of three nucleotides that code for an amino acid or act as a stop signal to tell the cell machinery when to halt protein translation. Codons are found in both DNA and messenger RNA, and a series of codons make up a gene.Full Answer >
The processes of DNA replication, gene transcription and protein translation are simpler in prokaryotes compared to eukaryotic cells. Ongoing scientific research is continually uncovering the complexities of these processes. Bacteria and other prokaryotes lack a nuclear envelope. Consequently, gene transcription and protein translation can take place simultaneously. All eukaryotic cells contain a membrane bound nucleus. By extension, transcription and translation are separated in space and time.Full Answer >
Codons are three-letter codes that make up the genetic code. Both RNA and DNA have triplets known as codons. Each codon codes one of 20 amino acids that the body uses to synthesize amino acids.Full Answer >
There are 64 different possible codons to the genetic code. Each codon is composed of three of the four genetic bases: guanine and adenine, which are the purine bases, and cytosine and thymine or uracil, the pyrimidine bases. A base may be repeated within a codon.Full Answer >