DNA & GENES (4A)

• Desc similarities and differences between RNA AND DNA

  • DNA is double helix & double stranded
  • RNA is single stranded
  • DNA is longer
  • DNA has deoxyribose sugar, RNA has ribose
  • DNA has Thymine base whereas RNA has uracil instead
  • Both are polymers of nucleotides
  • Both have phosphodiester bonds
• What is a gene?


  Sequence of DNA bases that code for a polypeptide
• How do bases help stabilise structure of DNA

  • Bases have H bonds in-between them to hold strands together
  • Many H bonds provides strength
• ADV for showing genetic code as base seq on RNA rather than triplets on DNA

  1. ribosomes assemble polypeptides using mRNA code
  2. DNA has 2 strands each with different complementary base sequence
• Name of 3 bases on a MRNA strand

  codon
• GENOME= Total number of genes in cell
• PROTEOME= Full range of proteins a cell can produce
• Define non coding sequences of DNA & Where are they found

  1. DNA that doesn't code for proteins/polypeptides
  2. Inbetween genes or on end of chromosome
• GENE= sequence of DNA bases that code for a protein
• EUKARYOTIC DNA VS PROKARY

  EUKARY

  • linear
  • wrapped around histones
  • long
  • Mitochondria and chloroplasts contain DNA

  PROKARY

  • circular
  • not associated with histones
  • shorter
  • Contains plasmids
• INTRONS= Sections of DNA that don't code for amino acids

  Removed via splicing at the end of transcription
• Human has 46 chromosomes (23 pairs)
• HOMOLOGUS PAIR= matching pairs of chromosomes that are the same size and have same genes- found at same locus
• GENETIC CODE= Sequence of base triplets in MRNA which codes for specific amino acids
• DEGENERATIVE= More than one triplet can code for an amino acid
• UNIVERSAL= Same triplets always code for the same amino acids in all living things
• NON OVERLAPPING= Each base is only apart of one triplet
• PRIMARY STRUCTURE OF PROTEIN= Sequence of amino acids joined by peptide bonds that code for a polypeptide