RNA and protein synthesis
The following factors must be present for DNA replication [replication: Production of an identical copy.] and transcription:
The base sequence in a DNA molecule, represented by the letters A T C G, make up the genetic code.
The bases hydrogen bond together in a complementary manner between strands. A will always go with T (U in RNA) and G will always go with C.
This code determines the type of amino acids and the order in which they are joined together to make a specific protein. The sequence of amino acids in a protein determines its structure and function.
The DNA code is a triplet code [triplet code: the genetic code made by a triplet of bases in the DNA chains: AAA; GCT; CAT etc] . Each triplet, a group of three bases, codes for a specific amino acid:
The main stages of protein synthesis are transcription and translation.
Transcription takes place in the nucleus:
Translation takes place on the ribosomes in the cytoplasm, or found on the rough Endoplasmic Reticulum (ER):
It is important to note that the tRNA is reused and collects another specific amino acid. Once the protein has been synthesised [synthesised: made or put together] mRNA may move to another ribosome to make a further protein or it can be broken down into free nucleotides to be reused.
After translation, the protein passes into the channels of the rough endoplasmic reticulum (ER) for transportation. The protein is then passed from the rough ER to the Golgi apparatus inside tiny fluid-filled sacs, called vesicles. The Golgi apparatus is a system of membranes [membrane: a very thin layer of tissue] , which are responsible for the modification, processing, and packaging of the proteins. The protein may have a carbohydrate added, to form a glycoprotein. The Golgi apparatus packages the protein in a secretory vesicle, which fuses with the cell membrane and releases the protein from the cell.
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