DNA structure

• what are monomers?

  atoms/small molecules that bond together to form more complex structures such as polymers
• what are the monomers of DNA?

  the DNA polymer is made up of repeating nucleotide units
• what are DNA nucleotides made up of?

  • red: common sugar
  • green: phosphate group
  • purple: one of four different bases: A, T, C, or G attached to the sugar

  
• how does a gene code for a particular amino acid?

  • sequence of 3 bases in a gene form a triplet
  • each triplet codes for an amino acid
  • the order of amino acids determine the structure & function of protein formed
• how do nucleotides interact to form a molecule of DNA?

  • sugar & phosphate molecules join to form a sugar-phosphate backbone in each DNA strand
  • base connected to each sugar
  • complementary base pairs joined by weak hydrogen bonds
  • A pairs with T
  • G pairs with C
• what is protein synthesis?

  the formation of protein from a gene
• what are the 2 stages of protein synthesis?

  1. transcription
  2. translation
• describe transcription

  • base sequence of gene copied onto a complementary template molecule (mRNA)
  • mRNA passes out of the nucleus into the cytoplasm
• describe translation

  • mRNA molecule attaches to a ribosome
  • amino acids are brought to ribosome on carrier molecules (tRNA)
  • ribosome reads triplet on mRNA & uses this to join together the correct amino acids in the correct order
  • protein chain folds into its unique shape
• why is the folding of amino acids important in proteins?

  when the protein chain is complete it folds up to form a unique shape which enables the proteins to carry out their function
• what is a mutation?

  • random change in the base sequence of DNA
  • most do not alter the protein
  • mutations occur continuously
• what is the effect of a gene mutation in coding DNA?

  • if it changes the amino acid sequence, the proteins structure & function may change e.g. enzyme may no longer fit substrate
  • if it doesn't change the amino acid sequence, there is no effect on protein structure & function
• what are non-coding parts of DNA?

  DNA which does not code for a protein but instead controls gene expression
• what is the effect of gene mutation in non-coding DNA

  gene expression may be altered, affecting protein production & the resulting phenotype