Transcription
Introduction: DNA transcription is the first step in protein synthesis, the creation of proteins for use in all aspects of the body. Occurring in the cell's nucleus, it is the sequencing (or transcribing) of RNA onto a DNA template using matching amino acids. Like in replication, the DNA strand serves as the template strand for assembling complementary sequences of nucleotides, but inside of creating more DNA the assembling strand is made up of RNA nucleotides. In RNA, the nucleotides are the same except that uracil (U) replaces thymine (T) and becomes the matching partner for adenine (A). Transcription is overall very similar to replication. Messenger RNA (mRNA), once built, is sent out of the nucleus and into the cytoplasm, where it enters the ribosomes to initiate translation.
RNA polymerase unwinds the helix at many different points along each DNA sequence, so that the two strands of nucleotides stand open as replication bubbles. Each side of the replication bubble, the point where the closed helix begins to open on each end, is the replication fork. New RNA nucleotides will build at each replication fork and cause it to keep expanding wider so that RNA can continue to build on the template strand. Ultimately, the opened bubbles will join together where they are forked when they have been unwound and expanded enough to meet each other.
RNA polymerase unwinds the helix at many different points along each DNA sequence, so that the two strands of nucleotides stand open as replication bubbles. Each side of the replication bubble, the point where the closed helix begins to open on each end, is the replication fork. New RNA nucleotides will build at each replication fork and cause it to keep expanding wider so that RNA can continue to build on the template strand. Ultimately, the opened bubbles will join together where they are forked when they have been unwound and expanded enough to meet each other.
Translation & Protein Synthesis
![Picture](/uploads/2/8/7/9/28799583/6993473.png?363)
Translation is the synthesis of a polypeptide, any type of protein, using information from mRNA. Ribosomes located in the cell's cytoplasm translate the nucleotide sequence of mRNA that has traveled there from transcription in the nucleus into the amino acid sequence of a polypeptide. Free-floating nucleotides join onto corresponding parts of the RNA chain. An enzyme factor connects these nucleotides, forming the amino acid chain that will break off of the ribosome and begin its various functions within the cell when completed.
Nucleotide sequences are translated into different amino acids based on what the codon, an ordered set of three nucleotides, codes for.
Chaperonins have a role in protein folding.
Be able to read a codon chart such as the one to the left. You should know how to identify the amino acid that a combination of three nucleotides codes for. Begin by looking for the nitrogenous base under the left-hand column that says First Letter that is the first letter in the codon, then find out which amino acid it codes for based on its second and third letters. This codon charts is helpful in identifying which proteins are being synthesize from a particular chain.
Nucleotide sequences are translated into different amino acids based on what the codon, an ordered set of three nucleotides, codes for.
Chaperonins have a role in protein folding.
Be able to read a codon chart such as the one to the left. You should know how to identify the amino acid that a combination of three nucleotides codes for. Begin by looking for the nitrogenous base under the left-hand column that says First Letter that is the first letter in the codon, then find out which amino acid it codes for based on its second and third letters. This codon charts is helpful in identifying which proteins are being synthesize from a particular chain.