BIOl1020  –  nucleic  acids  –  suppor5ng  slides  

Bacterial  cell   Animal  cell   Plant  cell  

DNA occurs in all living cells  

Bacterial  cell   Animal  cell   Plant  cell  

But  –  what  is  it  made  of,  and  how  can  informa5on  be  stored  in  this  molecule??  Pioneering  work:  Friedrich  Miescher  –  1869.  

DNA occurs in all living cells  

‘Nuclein’ is what we know today as Nucleic Acids

•  There are two types of nucleic acids –  Deoxyribonucleic acid (DNA) –  Ribonucleic acid (RNA)

•  DNA –  Stores information for the

synthesis of specific proteins –  Directs RNA synthesis –  Directs protein synthesis

through RNA

•  Central Dogma –  DNA-> RNA-> Protein

What do nucleic acids look like?

•  Nucleic acids exist as polymers called polynucleotides

•  Each polynucleotide consists of monomers called nucleotides

•  Nucleotides are connected by phosphodiester bonds

•  These bonds make the DNA strand directional (5’-3’)

•  The sequence of bases along a nucleotide polymer is unique for each gene

Note:    The  5’-­‐3’  end  designa5on  of  the  DNA  strand  is  based  on  the  atoms  of  the  pentose  sugar  in  the  backbone  

Nucleotides can contain five types of nitrogenous bases

•  Nucleotide monomers are made up of nucleosides and phosphate groups

•  There are five types of nitrogenous bases

•  DNA: A,T,C,G •  RNA: A,U,C,G

Inside  the  DNA  double  helix,  the  nitrogenous  bases  form  pairs  with  each  other  

•  Each  pair  contains  one  purine  and  one  pyrimidine  base  (which  is  which?)  

•  Only  two  types  of  pairs  are  formed:  A-­‐T  and  G-­‐C  

•  The  base  pairs  are  stabilized  by  either  two  or  three  hydrogen  bonds  

•  The  two  DNA  strands  are  complementary  to  each  other  

Inside  the  DNA  double  helix,  the  nitrogenous  bases  form  pairs  with  each  other  

•  Each  pair  contains  one  purine  and  one  pyrimidine  base  (which  is  which?)  

•  Only  two  types  of  pairs  are  formed:  A-­‐T  and  G-­‐C  

•  The  base  pairs  are  stabilized  by  hydrogen  bonds  

•  The  two  DNA  strands  are  complementary  to  each  other  

Other  DNA  proper5es:  

•  Both  DNA  and  RNA  for  extensive  secondary  structures  

•  Most  organisms  other  than  viruses  contain  double  stranded  DNA  

•  Double  stranded  DNA  strands  form  a  helical  structure.  –  Three  types:  A  &  B  form  (right  

handed  helices)  –  Z-­‐form  (le\  handed  helix)  –  B-­‐form  is  most  common  

B-­‐type  DNA