DNA and protein synthesis

• tRNA

  Clover leaf shape

  • Single stranded
  • Hydrogen bonding
  • Anticodon
  • Amino Acid binding site (requires ATP)
• mRNA

  Message makes sense

  • Codon
  • Single stranded
  • Exons without introns
  • Linear
• Transcription takes place in the nucleus
• Gene

  A base sequence of DNA that codes for

  • Amino acid sequence of a polypeptide
  • A functional RNA (ribosomal RNA and tRNA)
• Ribosome has 2 bonding sites to allow for amino acids to form a polypeptide chain
• Why is it called semi-conservative replication

  One new and one old strand.
• Frameshift

  One base is deleted; all amino acids are read one base faster downstream

  • Upstream; before mutation
  • Downstream; after mutation
• Mutagenic agents

  Increases rate of gene mutation
• Spindle fibres bind to centromeres
• Degenerate code

  More than one codon codes for the same amino acid
• Universal

  Each codon triplet always codes for the same amino acid in all organisms.
• Non-overlapping

  Each base in the sequence is read only once.
• Genome

  The complete set of genes in a cell
• Proteome

  Full range of proteins that a cell is able to produce.
• RNA polymerase joins mRNA nucleotides.
• Translation

  The production of polypeptides form the sequence of codons carried by mRNA.
• Homologous pairs

  Two chromosomes that carry the same genes

  • Not necessarily the same alleles of the genes.
• Diploid number

  Total number of homologous pairs.
• Any changes in the base sequence of a gene produces a new allele of that gene = mutation.


  Results in a different sequence of amino acids being coded for.

  • Base Substitution
  • Base Deletion
• Messenger RNA

  Transfers DNA from the nucleus to the cytoplasm
• Codon

  Refers to the sequence of three bases on mRNA that codes for a single amino acid.
• Complete proteome

  Proteome refers to the proteins produced by a given type of cell under a certain set of conditions.
• Ribonucleic Acid (RNA)

  Polymer made of a single nucleotide chain

  • Pentose sugar ribose
  • One organic base
  • A phosphate group.
• Homologous chromosomes

  A pair of chromosomes, one maternal and one paternal, that have the same gene loci
• Independent segregation

  Chromosomes line up alongside its homologous partner at random.

  • The combination of chromosomes that go into daughter cells is a matter of chance.
• Crossing over.

  Chromosome lines up alongside its homologous partner.

  • Chromatids of each pair synapse and forms chiasmata
• Chiasmata

  Holds chromosomes together

  • Allows for crossing over and exchange of alleles.
• Meiosis produces daughter cells that are genetically different from each other.
• Mutations in the number of chromosomes can arise spontaneously by chromosome non-disjunction.
• Base Deletion

  A base is deleted

  • Causes a frame shift
• Base Substitution

  Substitution of a base

  • Different amino acid made
  • Effect of mutation will differ
• Prophase

  DNA condenses; thicker / shorter; become visible

  • Two sister chromatids joined together by a centromere
  • Arranged side by side in homologous pairs
  • Spindle fibres develop from centrioles
  • Centrioles move to opposite ends
  • Nuclear envelope breaks down.
• Metaphase

  Chromosomes align along the equator

  • Spindle fibres attach to chromosomes by their centromeres.
• Anaphase

  Chromatids pulled to opposite poles of the cells

  • Centromeres divide
  • Spindle fibres shorten / contract
• Telophase


  Nucleolus and nuclear envelope reform = 2 nuclei

  • Chromosomes uncoil; longer / thinner
  • Spindle fibres/ centrioles break down