What do codons mean?
Listen to pronunciation. (KOH-don) In DNA or RNA, a sequence of 3 consecutive nucleotides that codes for a specific amino acid or signals the termination of gene translation (stop or termination codon).
Is methionine always the first amino acid?
Because the first tRNA to bind to the peptidyl binding site (P site) in the initiation complex is always the initiator tRNA, tRNAfMET. tRNAfMET binds to the start codon of mRNA, AUG. The first amino acid of the protein is thus methionine.
How does mRNA turn into a protein?
The type of RNA that contains the information for making a protein is called messenger RNA (mRNA) because it carries the information, or message, from the DNA out of the nucleus into the cytoplasm. Through the processes of transcription and translation, information from genes is used to make proteins.
How is mRNA translated?
Thus, mRNAs are usually translated by a series of ribosomes, spaced at intervals of about 100 to 200 nucleotides (Figure 7.14). The group of ribosomes bound to an mRNA molecule is called a polyribosome, or polysome. Each ribosome within the group functions independently to synthesize a separate polypeptide chain.
What is an example of a codon?
An example of a codon is the sequence AUG, which specifies the amino acid methionine. The AUG codon, in addition to coding for methionine, is found at the beginning of every messenger RNA (mRNA) and indicates the start of a protein.
Why do all proteins not begin with methionine?
The short answer is because the “start codon” AUG codes for Methionine, all proteins must start with Methionine. The longer answer is that mRNA is tranlated (turned into protein) by the ribosome. There’s also a molecule called a tRNA that carries the amino acid about to be added to the protein.
How does RNA differ from DNA?
There are two differences that distinguish DNA from RNA: (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type of ribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine.