Structure of RNA and DNA

• Two types of Nucleic acids:

  
  

  DNA

  RNA
• DNA stands for deoxyribonucleic acid
• DNA holds all the genetic information in a cell
• RNA stands for ribonucleic acid
• RNA acts as a messenger between DNA and ribosomes for the synthesis of proteins
• Ribosomes are formed from RNA and proteins
• Nucleotides are made up of three things :

  
  

  a phosphate group

  a pentose sugar

  and a nitrogenous base
• the phosphate group in a nucleotide is never specified
• In DNA the pentose sugar is deoxyribose
• The nitrogenous bases in DNA are:

  
  

  Adenine

  Thymine

  Cytosine

  Guanine
• In DNA : Adenine is complimentary to Thymine
• Cytosine is complimentary to Guanine
• hydrogen bonding between the nitrogenous bases hold the two strands of DNA , therefore creating a double helix
• In RNA , the pentose sugar is ribose
• The nitrogenous bases in RNA are :

  
  

  Adenine

  Uracil

  Cytosine

  Guanine
• A condensation reaction between two nucleotides forms a phosphodiester bond
• In RNA , adenine is complimentary to uracil
• polynucleotides form from a condensation reaction between nucleotides which form phosphodiester bonds
• DNA's structure is a double helix of 2 polynucleotide strands , has hydrogen bonds between its base pairs
• DNA is a long molecule that stores lots of information , has weak Hydrogen bonds which break easily so strands separate for replication
• structure of RNA : single stranded and contains uracil instead of thymine
• RNA functions :

  breaks down quickly so no excess polypeptide forms

  can be translated into a specific polypeptide by ribosomes
• semi conservative :

  strands from original DNA molecule act as a template , new DNA molecule contains 1 old strand & 1 new strand
• a phosphodiester bond is a condensaton reaction between phosphate and deoxyribose

  is catalysed by DNA polymerase