The Genome

Cards (23)

  • DNA
    A double-stranded polymer of nucleotides, wound to form a double helix
  • What are the monomers of DNA?
    Nucleotides
  • What are DNA nucleotides made up of?
    Common sugar
    Phosphate group
    • One of four bases : A, T, C or G
  • Names of the bases found in nucleotides
    Adenine
    Thymine
    Cytosine
    Guanine
  • Desc how nucleotides in to form a molecule of DNA
    Sugar and 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
  • Chromosome
    A long, coiled molecule of DNA that carries genetic in in the form of genes
  • Describe the method used to extract DNA from fruit
    1. Place the piece of fruit in a beaker and crush it
    2. Add detergent and salt, mix
    3. Filter the mixture and collect the liquid in a test tube
    4. Pour chilled ethanol into the test tube
    5. DNA precipitates forming a fibrous white solid
    6. Use a glass rod to collect the DNA sample
  • Why is detergent added to the crushed fruit?
    To break down cell membranes and release DNA into the solution
  • Why is salt added to the crushed fruit?
    Salt encourages the precipitation of DNA
  • Explain how a gene codes for a protein
    • A sequence of three bases in a gene forms a triplet
    • Each triplet codes for an amino acid
    • The order of amino acids determines the structure (i.e. how it will fold) and function of protein formed
  • Why is the ‘folding’ of amino acids important in proteins such as enzymes?
    It determines the shape of the active site which must be highly specific to the shape of its substrate
  • What is protein synthesis?
    The formation of a protein from a gene
  • What are the two stages of protein synthesis?
    Transcription and translation
  • What does transcription involve?
    Transcription involves the process of converting DNA into RNA
  • Transcription
    1. DNA double helix unwinds
    2. RNA polymerase binds to a specific base sequence of non-coding DNA in front of a gene and moves along the DNA strand
    3. RNA polymerase joins free RNA nucleotides to complementary bases on the coding DNA strand
    4. mRNA formation complete
    5. mRNA detaches and leaves the nucleus
  • Differences between mRNA and DNA
    • mRNA is single stranded whereas DNA is double stranded
    • mRNA uses U whereas DNA uses T
  • Why is mRNA used in translation rather than DNA?
    DNA is too large to leave the nucleus so cannot reach the ribosome
  • What does translation involve?
    A ribosome joins amino acids in a specific order dictated by mRNA to form a protein
  • How is a tRNA molecule adapted to its function?
    Each tRNA molecule has an anticodon which is specific to the codon of the amino acid that it carries
  • Mutation
    A random change in the base sequence of DNA which results in genetic variants
  • Describe the effect of a gene mutation in coding DNA
    • If a mutation changes the amino acid sequence, protein structure and function may change
    • If a mutation does not change amino acid sequence, there is no effect on protein structure or function
  • What is non-coding DNA?
    The portions of DNA that do not code for proteins
  • Describe the effect of a gene mutation in non-coding DNA
    • A mutation may affect the ability of RNA polymerase to bind to non-coding DNA
    • This may affect protein production and the resulting phenotype of the organism