NUCLEIC ACIDS AND PROTEIN SYNTHESIS

• Nucleic acids


  are unbranched polymers composed of repeating monomers called nucleotides
• DNA


  Stores the genetic information of an organism and transmits that information from one generation to another.
• RNA


  Translates the genetic information contained in DNA into proteins needed for all cellular functions.
• Nucleoside


  is formed by joining a carbon of the monosaccharide with a nitrogen atom of the base.
• Primes


  are used to number the carbons of the monosaccharide in a nucleoside.
• James Watson and Francis Crick

  Our current understanding of the structure of DNA is based on the model proposed initially by them
• Complementary base pair


  Two bases hydrogen bond together in a predictable manner
• Replication 


  the process by which DNA makes a copy of itself when a cell divide
• Transcription


  the ordered synthesis of RNA from DNA. In this process, the genetic information stored in DNA is passed onto RNA
• Translation


  the synthesis of proteins from RNA. In this process, the genetic message contained in RNA determines the specific amino acid sequence of a protein.
• Leading strand


  Strand that grows continuously in DNA replication
• Lagging strand 


  Strand that synthesized in small fragments, which are then joined together by an enzyme in DNA replication
• Helicase


  Unwinds a portion of the DNA double helix
• RNA primase


  Attaches RNA primers to the replicating strand
• DNA polymerase delta


  Binds to the 5'-3' strand in order to bring nucleotides and create the daughter leading strand.
• DNA polymerase epsilon


  Binds to the 3' - 5' strand in order to create discontinuous segments starting from different RNA primers.
• Exonuclease


  Finds and removes the RNA primers
• DNA ligase


  Adds phosphate in the remaining gaps of the phosphate - sugar backbone
• Nuclease


  Removes wrong nucleotides from the daughter strands
• Ribosomal DNA


  the most abundant type of RNA, is found in the ribosomes in the cytoplasm of the cell.
• Messenger RNA


  the carrier of information from DNA to the ribosomes
• Transfer RNA


  the smallest type of RNA, interprets the genetic information in mRNA and brings specific amino acids to the site of protein synthesis in the ribosome
• codon


  A sequence of three nucleotides (a triplet) codes for a specific amino acid
• mRNA 


  Contains the sequence of codons that determines the order of amino acids in the protein
• Individual tRNAs


  bring specific amino acids to add to the peptide chain.
• tRNA


  contains binding sites that provide the platform on which protein synthesis occurs
• Initiation 


  consists of the binding of the ribosomal subunits to mRNA and the arrival of the first tRNA carrying its amino acid
• Elongation


  The protein is synthesized. One by one a tRNA with its designated amino acid binds to a site on the ribosome adjacent to the first tRNA. A peptide bond forms and a tRNA is released. The ribosome shifts to the next codon and the process continues.
• Termination 


  occurs when a stop codon is reached. The synthesis is complete and the protein is released from the complex.
• Mutation 


  a change in the nucleotide sequence in a molecule of DNA.
• Mutagens 


  are chemical substances that alter the structure of DNA.
• Point mutation


  the substitution of one nucleotide for another.
• deletion mutation


  occurs when one or more nucleotides is lost from a DNA molecule.
• insertion mutation


  occurs when one or more nucleotides is added to a DNA molecule.
• DNA fingerprinting


  used as a method of identification. The DNA is cut into fragments with various enzymes and the fragments are called separated by size using a technique gel electrophoresis. DNA fragments can be visualized on X-ray film after they react with a radioactive consisting of obe. The result is an image set of horizontal bands, each band corresponding to a segment of DNA, sorted from low to high molecular weight.
• virus 


  an infectious agent consisting of a DNA or RNA molecule that is contained within a protein coating.
• retrovirus


  a virus that contains a core of RNA
• reverse transcription


  Once a retrovirus invades a host organism, it must first make DNA by this process
• vaccine


  an inactive form of a virus that causes an individual's immune system to produce antibodies to the virus to ward off infection