Genetics

• Broad categories of cells

  • Prokaryotic cells
  • Eukaryotic cells
• Prokaryotic cells

  • Single-celled organisms of the domains Bacteria and Archaea
  • Do not contain a membrane-bound nucleus or organelles
• Eukaryotic cells

  • Multicellular organisms including animals, plants, fungi and protists
  • Do contain a membrane-bound nucleus and organelles
• Key components shared by all cells

  • Cytoplasm
  • Cell membrane
  • DNA
  • Ribosomes
• Cytoplasm

  The jelly-like cytosol (liquid) inside the cell, plus the cellular structures suspended in it
• Cell membrane

  The selectively-permeable outer covering that separates the cell from its surrounding environment, while taking in nutrients and removing waste
• DNA

  The set of instructions that contain all the information that enable the cell to survive
• Ribosomes

  Molecular machines that synthesize proteins
• Prokaryote cells

  • Simple cells
  • Bacteria
  • DNA is circular and floats in the cytoplasm
  • Some have a flagella to help them move
  • Some have a capsule to avoid the body's immune system
• Eukaryotic cells

  • Larger than prokaryotes
  • Contain a membrane-bound nucleus
  • Contain a number of membrane-bound organelles
• Mitosis

  Production of two daughter cells that are genetically identical to the parent (original) cell
• When does mitosis occur?

  • During growth
  • During asexual reproduction when it is important that each daughter has the same chromosomes (and same genes)
• Importance of mitosis

  • New cells must be identical to existing ones
  • Damaged or old cells must be replaced with identical cells
• Stages of mitosis

  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokinesis
• Interphase

  • The amount of DNA in the nucleus doubles by a process called DNA replication
  • Also known as the "in between phase"
  • New organelles are made for the new cell
• Prophase

  • Condensing and visibility of chromosomes within the nucleus
  • Chromosomes become visible
  • Spindle forms in the cytoplasm and starts to interact with chromosomes
• Metaphase

  • Breaking down of the nuclear membrane
  • Chromosomes move to the equator (center) of the cell and line up ready to separate
• Anaphase

  • Splitting of the chromosomes into two identical chromatids
  • Chromatids move to the opposite ends of the spindle
• Telophase

  • New nuclear membranes form around each of the two sets of chromosomes
  • Chromatids are at each end of the poles
  • Chromosomes start to change back to long strands of DNA
• Genes (your DNA) contain the instructions for building a human with all your unique physical qualities
• Gene

  A sequence of DNA which codes for a protein (or RNA)
• Chromosome

  Tiny thread-like structures inside the nucleus of a cell that contain the DNA that carries genetic information
• DNA (deoxyribonucleic acid)


  The chemical substance found in all living things that encodes the genetic information of an organism
• Nucleus

  A membrane-bound organelle containing the genetic material DNA
• Characteristics of chromosomes and genes

  • Chromosomes are packets of coiled up DNA
  • Humans have 23 pairs of chromosomes, half from mother and half from father
  • Genes are parts of DNA molecules coded to create one protein
  • Each DNA molecule contains many genes
• Mutations

  • Alterations in the DNA of chromosomes
  • May be neutral or 'silent' (no observable effect)
  • Harmful mutations alter the survival capacity of the organism
• Causes of mutations

  • Occur randomly and spontaneously
  • Induced by environmental factors
• Types of mutations

  • Acquired (somatic) mutations in body cells not passed to offspring
  • Hereditary mutations in gametes passed to offspring
• Types of chromosome mutations

  • Deletion
  • Translocation
  • Inversion
  • Duplication
  • Non-disjunction
• Deletion

  Loss of one or more nucleotides from a segment of DNA, can cause severe congenital anomalies and disability
• Inversion

  A chromosome breaks in two places, the resulting DNA piece is reversed and re-inserted, less severe impact than deletion
• Duplication

  One or more copies of a DNA segment are produced, can cause Down syndrome
• Non-disjunction

  Chromosomes fail to separate correctly during anaphase, resulting in gametes with one extra or one missing chromosome
• Types of gene mutations

  • Substitution
  • Silent mutation
  • Missense mutation
• Point mutations occur when a single base pair is added, deleted or changed in the genome
• Duplication

  A type of mutation in which one or more copies of a DNA segment (which can be as small as a few bases or as large as a major chromosomal region) is produced
• Non-Disjunction

  Chromosomes failing to separate correctly during anaphase 1 or 2, resulting in gametes with one extra, or one missing, chromosome (aneuploidy)
• Point mutations

  Occurs in a genome when a single base pair is added, deleted or changed
• Types of point mutation

  • Substitution
  • Silent mutation
  • Missense mutation
  • Non-sense mutation
• Substitution

  The wrong base is matched together