DNA and Protein Synthesis

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RNA RECAP!
RNA stands for RIBONUCLEIC ACID.It's made up of Ribose, Phosphate group, organic bases.The 4 Organic Bases are: ADENINE, URACIL, CYTOSINE, GUANINE.The Pentose sugar is RIBOSEA monomer of this molecule is called a NUCLEOTIDEThe bond that join these monomers together is a PHOSPHODIESTER BOND.The bond is a result of a CONDENSATION REACTION.

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Similarities of MRNA and TRNA
-Both Single Stranded-Both Have Ribose Sugar-Both Have Same bases

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The Genetic Code is described as Universal, what does this mean?-Genetic Code= universal as it appears to be the SAME in all organisms. Why do we believe that the genetic code is a triplet code?A DNA TRIPLET CODE is the Smallest coding unit that can accommodate the 20 A.A that make up the variety of proteins.What are stop codons and how many are there? [Do not code for anything]3 of the possible 3-letter codons fail to specify an A.A; such triplets are STOP CODONS and indicate the end of the genetic message in a gene. In MRNA:                    [UAA, UAG, UGA]What is the significance of the AUG CODON?The AUG codon is the START CODON and is found at the start of all the genes. Why is the genetic code described as non-overlapping.The GC is non-overlapping being read in groups of 3 bases with no overlap between the codons. Why is the genetic code described as degenerate?An amino acid may be coded for more than 1 triplet code.    E.g.  ATA|CGG  both code for the same amino acid. 
Polypeptide Synthesis,DNA terms/concepts

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3 Types of RNA
MRNA:-Rna mols that Convey genetic info from DNA to Ribosome.TRNA:-Rna mols-help decode an mrna sequence into a protein. Rrna:-Rna component of the ribosome. Proteome: The full range of proteins a cell is able to produce  Exon: Section of DNA that codes for amino acids.Introns: Section of DNA that does not code for amino acids.

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Polypeptide Synthesis -Transcription
The process of making pre-MRNA using part of the DNA as a template.   UTRPRDIL      1.) Section of DNA unzips- H bonds being broken by the enzyme DNA HELICASE.2.) One of the exposed strands of DNA becomes a template (template strand) and nucleotides of RNA present in the nucleus attach to complementary DNA nucleotides (T being replaced by U).3.) Enzyme RNA POLYMERASE joins RNA nucleotides together to form a single strand of MRNA.4.) As a strand of pre-MRNA is formed by RNA polymerase moving along the DNA, the DNA zips back up behind the enzyme. (only 12 DNA bases exposed at any one time.)5.) When RNA POLYMERASE reaches a STOP CODON, it detaches from the DNA and the production of pre-MRNA is then complete.6.) DNA is constructed from INTRONS (not code for amino acids) and EXONS (Code for amino acids)   [Prokaryotes=not have Introns]. Introns are unnecessary to the structure of the MRNA and would interfere with polypeptide formation, therefore are removed in SPLICING. (exons are joined together when introns are removed)7.) The MRNA leaves the nucleus through a pore in the nuclear membrane (as MRNA mols are too large to diffuse out of the nucleus). Outside the nucleus, the MRNA is attracted to the ribosomes, to which it becomes attached, ready for translation. 

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Translation
During Translation, the entire message in MRNA is read CODON-BY-CODON [non overlapping] until the polypeptide chain is completely assembled according to the instructions originally encoded in the DNA.The process of translation involves MRNA, Amino Acids, Ribosomes, A variety of enzymes, and chemical energy in the form of ATP.Translation also requires TRNA that decodes MRNA's message and translates it into the language of proteins. TRNA is referred to as a Decoder Molecule.There are a variety of unique TRNA mols that differ from one another in the triplet of bases at one end of the mol called the anticodon. 
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TRANSLATION
1.) Ribosome attaches to start of MRNA mol.[3 bases on the MRNA mol form a codon and 2 codons fit into ribosome at once.]2.) TRNA mol with complementary anticodons to the MRNA codons enter Ribosome. They bring their specific amino acids. 3.) The 2 A.A carried by the TRNA mols come very close to one another. They join to each other by a peptide bond- this requires energy in the form of ATP.4.) The first TRNA is now released from the A.A. It leaves the Ribosome and can now bring another A.A of the same kind to the Ribosome. 5.) The Ribosome moves along the MRNA, and a new TRNA enters the ribosome, bringing its A.A.6.) This process continues until the Ribosome reaches a STOP or non-sense codon which does not code for an amino acid.

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