Nucleic acids

• There are two types of nucleic acids –

  deoxyribonucleic acid (DNA)

  and ribonucleic acid (RNA).

  These 2 molecules have the role of the control of cells/organisms (building proteins)
• Nucleotides – nucleic acids are built up from repeating units called

  nucleotides. A nucleotide consists of three substances combined together –

  ● A nitrogenous base, either cytosine, guanine, adenine, thymine or

  uracil

  ● A pentose sugar, either ribose or deoxyribose

  ● Phosphoric acid (also called phosphate)
• Nucleotides join together by condensation reactions to form huge molecules – the nucleic acid, also known as polynucleotides.
• nucleic acids alternate sugar and phosphate groups form the

  backbone to the nucleic acid.

  These are joined by phosphodiester bonds which link adjacent nucleotides together making a nucleic acid strand.

  A nitrogenous base attaches to each sugar along the strand.
• differences in DNA and RNA:

  RNA are shorter than DNA

  RNA nucleotides include ribosome

  RNA bases are cytosine, adenine, uracil and guanine, but NEVER THYMINE (uracil and thymine swaps)

  RNA is always a single strand
• ALL RNA IS INVOLVED IN PROTEIN SYNTHESIS
• messenger rna (mRNA) carries the code from the DNA in the nucleus where it is protected (less likely to mutate the nuclues), to a ribosome in the cytoplasm where protein synthesis takes place.
• Transfer RNA (tRNA) - carries animo acid to the ribosome complex where protein synthesis takes place.

  It is a single stranded chain folded into a clover leaf shape. Each tRNA has a similar shape BUT a unique part that codes for a specific a.a. In

  practice each a.a. has its own tRNA.
• Ribosomal RNA (rRNA) is made in the nucleolus and forms over half of the mass of each ribosome.
• DNA molecules in chromosomes form very long strands.

  DNA nucleotides have deoxyribose

  DNA bases are cytosine, guanine, adenine and thymine NEVER URACIL.
• DNA molecules have polynucleotide strands (double stranded molecule)

  
  

  held by H2 BONDS

  double helix shape

  The DNA strands are wound around a protein called Histone- this structure has DNA coiled around it.
• The pairing of bases is between adenine and thymine, and between cytosine and guanine, because they are the only combinations of bases that will fit together within the helix. This pairing, known

  as complimentary base pairing, is the key to the way information is held in the nucleic acids, and the form in which it is transferred to mRNA to be used in the cytoplasm.
• DNA functions - coding template
• DNA is the genetic code responsible for protein synthesis, specifically the regulation of enzymes, key catalysts. The sequence of DNA determines the amino acid sequence (primary structure) of polypeptides.
• Gene - a sequence of DNA that codes for a particular polypeptide.
• In a gene one of the two strands is known as the coding/template strand. This is the genetic code and is read as a sequence of bases . Each three bases being known as a base triplet, and coding for an a.a.