higher biology unit 1

• Somatic cell


  Any cell in the body other than cells involved in reproduction
• Germline cell


  Gametes and stem cells that divide to form gametes
• Cellular differentiation


  When a cell expresses certain genes to produce protein characteristics for that type of cells
• Stem cells

  Unspecialised body cells
• Stem cells


  • Multipotent, growth, repair & renewal of cells
• Embryonic stem cells


  Very early embryo, pluripotent
• Therapeutic stem cells


  Regeneration of damaged skin, Corneal repair
• Cancer cells


  • Do not respond to regulatory signals, Divide excessively, Mass of abnormal cells are called a tumour, Fail to attach so spread throughout the blood around the body
• DNA


  Deoxyribose sugar, a phosphate, a base joined together by a sugar-phosphate bond
• DNA replication


  1. DNA unwinds and hydrogen bonds are broken

  2. DNA polymerase add DNA nucleotides from the 3' end

  3. Leading strand being continuously replicated and a lagging strand being replicated in fragments

  4. Ligase joins the fragments together
• PCR (Polymerase Chain Reaction)


  Amplifies DNA using complementary primers
• PCR repeated cycles


  1. DNA heated to 92°C to separate strands

  2. Cooled to 50°C to allow primers to bind

  3. Heated to 70°C for DNA polymerase to replicate the DNA
• Types of RNA


  • mRNA
  • tRNA
  • rRNA
• mRNA function


  Carries a copy of DNA code from nucleus to the ribosome
• tRNA function


  Carries a specific amino acid to the ribosome
• rRNA function


  Forms ribosomes with CRNA and proteins
• Transcription


  1. RNA polymerase unwinds and breaks hydrogen bonds

  2. RNA polymerase synthesises a primary transcript of mRNA by complementary base pairing
• Exons


  Coding regions
• Introns


  Non-coding regions
• Splicing


  When introns are removed, and exons are joined together (order of exons remain unchanged)
• Translation


  1. Begins at start codon, ends at stop codon

  2. tRNA carries a specific amino acid to the ribosome

  3. Anticodons bond to codons, translating into a sequence of amino acids

  4. Amino acids join with peptide bond to form a polypeptide
• Alternative RNA splicing

  Some different exons retained from primary transcript
• What holds together the three-dimensional shape of a protein

  Hydrogen bonds, and interactions of amino acids
• Types of single gene mutations


  • Substitution
  • Insertion
  • Deletion
  • Insertion & deletion at the same time
• Types of single nucleotide substitutions


  • Missense
  • Nonsense
  • Splice-site
• Types of chromosome mutations


  • Deletion
  • Duplication
  • Inversion
  • Translocation
• Genome


  The entire hereditary information encoded in DNA
• Genome composition


  Genes and other DNA sequences
• Why genomes can be analysed


  To predict the likelihood of developing diseases
• Pharmacogenetics


  The use of genome information in the choice of drug, selecting the most effective drug and dosage
• Metabolic pathways

  Controlled pathways of enzyme-catalysed reactions
• Anabolic reactions


  Build up, require energy
• Catabolic reactions


  Breakdown, release energy
• Induced fit


  The active site changes shape to better fit the substrate after it binds
• Why products leave the active site

  They have a low affinity
• Competitive inhibitor


  Binds to the active site, can be reversed
• Non-competitive inhibitor


  Binds away from the active site, changes its shape, irreversible