Gene Expression
Gene expression is the entire process that takes the information contained in genes on DNA and turns that information into proteins.
Transcription is the transfer of the genetic information from the archival copy of DNA to the short-lived messenger RNA. The enzyme RNA polymerase binds to a particular region of the DNA and starts to make a strand of mRNA wiht a base sequence complementary to the DNA template that is "downstream" of the RNA polymerase binding site. When this transcription is finished, the portion of the DNA that coded for a protein, i.e. a gene, is now represented by a messenger RNA molecule that can be used as a template for translation.
The steps in transcription are:
1.DNA unzips and RNA polymerase enzyme binds to one strand of DNA
2.RNA polymerase makes an elongating chain of RNA nucleotides, each new RNA nucleotide complementary to the DNA nucleotide it is hydrogen bonded to
3.The completed mRNA molecule is released from RNA polymerase - DNA complex and can begin translation. In eukaryotic cells this means first moving from the nucleus into the cytoplasm. In prokaryotic cells (bacteria), ribosomes can bind and begin translation before polymerase has completed of the new mRNA strand.
Translation
Translation is the process that takes the information passed from DNA as messenger RNA and turns this into a series of amino acids bound together with peptide bonds. It really is a translation from one code, nucleotide sequence, to another code, amino acid sequence. The ribosome is the site of this action, just as RNA polymerase was the site of mRNA synthesis. The ribosome matches the base sequence on the mRNA in sets of three bases (called codons) to tRNA molecules that have the three complementary bases in their anticodon regions. Again, the base pairing rule is important in this recognition (A binds to U and C binds to G). The ribosome moves along the mRNA, matching 3 base pairs at a time and adding the amino acids to the polypeptide chain. When the ribosome reaches one of the "stop" codes, the ribosome releases both the polypeptide and the mRNA. This polypeptide will twist into its native coformation and begin to act as a protein in the cells metabolism. This may be a binding protein, an enzyme, a membrane channel or transport site, or part of the electron transport chain. This description is for the simplest case such as some examples of bacterial protein synthesis. Eukaryotic cells follow these steps but other control steps and modifications are common.
The steps in translation are:
the ribosome binds to mRNA at a specific area
the ribosome starts matching tRNA anticodon sequences to the mRNA codon sequence
each time a new tRNA comes into the ribosome, the amino acid that it was carrying gets added to the elongating polypeptide chain
the ribosome continues until it hits a stop sequence, then it releases the polypeptide and the mRNA
the polypeptide forms into its native shape and starts acting as a functional protein in the cell
Translation is the process that takes the information passed from DNA as messenger RNA and turns this into a series of amino acids bound together with peptide bonds. It really is a translation from one code, nucleotide sequence, to another code, amino acid sequence. The ribosome is the site of this action, just as RNA polymerase was the site of mRNA synthesis. The ribosome matches the base sequence on the mRNA in sets of three bases (called codons) to tRNA molecules that have the three complementary bases in their anticodon regions. Again, the base pairing rule is important in this recognition (A binds to U and C binds to G). The ribosome moves along the mRNA, matching 3 base pairs at a time and adding the amino acids to the polypeptide chain. When the ribosome reaches one of the "stop" codes, the ribosome releases both the polypeptide and the mRNA. This polypeptide will twist into its native coformation and begin to act as a protein in the cells metabolism. This may be a binding protein, an enzyme, a membrane channel or transport site, or part of the electron transport chain. This description is for the simplest case such as some examples of bacterial protein synthesis. Eukaryotic cells follow these steps but other control steps and modifications are common.
The steps in translation are:
the ribosome binds to mRNA at a specific area
the ribosome starts matching tRNA anticodon sequences to the mRNA codon sequence
each time a new tRNA comes into the ribosome, the amino acid that it was carrying gets added to the elongating polypeptide chain
the ribosome continues until it hits a stop sequence, then it releases the polypeptide and the mRNA
the polypeptide forms into its native shape and starts acting as a functional protein in the cell