Key Questions 3

• Prokaryotic DNA


  Short, Circular, not associated with histone proteins
• Eukaryotic DNA


  Long, Linear, associated with histone proteins
• Organelles other than the nucleus that have DNA

  • Mitochondria
  • Chloroplasts
• DNA found in Mitochondria


  Short, Circular, not associated with histone proteins
• Gene


  A base sequence of DNA that codes for a polypeptide or functional RNA
• Locus


  The position of a gene on a chromosome
• Degenerate code


  When more than one triplet code codes for the same amino acid
• Non-overlapping


  The DNA code is read in triplets and then the next three triplets are read
• Universal


  The triplet code codes for the same amino acid in all organisms
• Exon


  A sequence of DNA that codes for a polypeptide
• Intron


  A non-coding sequence that is found within a gene
• Histone


  Circular proteins that combined with DNA to make a chromosome
• Stages of cell division

  • Nuclear division
  • Cytokinesis
• Nuclear division


  A process by which the nucleus divides
• Cytokinesis


  A process by which the whole cell divides
• Nucleotides in DNA


  • Adenine
  • Guanine
  • Cytosine
  • Thymine
• DNA helicase


  Breaks the hydrogen bonds between opposing nucleotides
• DNA polymerase


  Joins adjacent nucleotides together forming phosphodiester bonds
• DNA


  Deoxyribonucleic acid
• Complementary base pairing


  Adenine always pairs with Thymine, and Cytosine always pairs with Guanine
• Part of DNA nucleotide containing nitrogen

  The base
• Isotope


  When an atom can have different atomic masses or when a molecule has the same molecular formula, but a different structure
• Types of cell division

  • Mitosis
  • Meiosis
• Mitosis


  Cell division which produces two daughter cells which have the same number of chromosomes as the parent cell, both are genetically identical
• Meiosis


  Cell division which produces four daughter cells each with half the number of chromosomes as the parent's cell and are all genetically different
• Gene mutation


  A change in the order or number of nucleotides in a gene
• Centromere


  What joins two chromatids together in a chromosome
• Phases of mitosis


  • Interphase
  • G1 phase
  • S phase
  • G2 phase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• Interphase


  The cell carries out normal cellular activity including G1, S, G2 phase
• G1 phase


  The cell grows to its normal size after the previous division
• S phase


  The cell undergoes DNA replication
• G2 phase


  The cell produces new organelles specific for division
• Prophase


  The chromosomes become visible as they shorten and thicken. Centrioles start to move to the poles of the cell
• Metaphase


  The chromosomes are pulled using spindle fibres to the equator of the cell
• Anaphase


  The centromere divides, the spindle fibres get shorter and the chromatids move to the opposite poles of the cell
• Telophase

  The chromatids unravel and the nuclear envelope reforms
• Binary fission


  Cell division in prokaryotic cells
• Cytokinesis


  Division of the cytoplasm to produce 2 cells
• Importance of mitosis


  Growth of new tissues. Repair of tissues. Reproduction of single celled eukaryotes. Asexual reproduction
• What viruses use to enter host cell

  Attachment proteins