Topic 1 You and Your Genes

• Genome


  The entire genetic material of an organism
• Chromosome


  A thread-like structure of DNA that carries genetic information in the form of genes
• Gene


  A length of DNA that codes for a particular protein
• Allele


  One of a number of different versions of a gene
• Genotype


  The genetic makeup of an organism, consisting of all the alleles present
• Phenotype


  The observable features of an organism as a result of the expression of particular alleles of the gene and interaction with the environment
• Eukaryotic cells


  • Contain a nucleus and membrane bound organelles such as ribosomes and mitochondria
• Prokaryotic cells


  • Do not contain a nucleus and membrane bound organelles
• Plasmids


  Circular loops of DNA found in the cytoplasm of prokaryotic cells
• In eukaryotes, DNA is stored in the nucleus
• Most characteristics of an organism are determined by the genome
• Dominant allele


  An allele that will be expressed if present in the genome
• Characteristics can also be influenced by external factors as the organism interacts with the environment
• DNA


  Deoxyribonucleic acid, acts like instructions allowing the cell to carry out a variety of key processes
• Protein synthesis


  Amino acids are bonded together to make proteins
• DNA


  A polymer made up of many nucleotide monomers bound together in a chain, forming two long strands which wind around each other to form a double helix
• Types of nucleotides in DNA

  • Common sugar
  • Phosphate group
  • One of four different bases
• Protein synthesis


  1. mRNA strand is made from a section of DNA

  2. mRNA exits the nucleus and travels to a ribosome

  3. Ribosome uses mRNA to join amino acids in a specific order to produce a particular protein
• Mutation


  A genetic change which results in a change in the sequence of DNA bases (nucleotides)
• Mutations can occur due to exposure to chemicals and ionising radiation
• Mutations can alter how genes function, leading to new alleles and genetic variation
• Inheritance


  The transmission of genetic information from parents to offspring
• Gamete


  A reproductive cell which carries one half of each chromosome pair
• Homozygous


  An organism containing two identical alleles of a particular gene
• Heterozygous


  An organism containing two different alleles of a particular gene
• Dominant allele


  A dominant allele, if present in an organism, is always expressed in the phenotype and will mask recessive alleles
• Recessive allele


  Recessive alleles are only expressed in the phenotype in the absence of a dominant allele
• Single gene inheritance


  Offspring inherit characteristics from both parents

  2. If parents have same allele, offspring are homozygous

  3. If parents have different alleles, offspring are heterozygous

  4. Dominant alleles are always expressed, recessive alleles only expressed if no dominant allele present
• Single gene crosses


  Dominant allele written as capital letter, recessive as lowercase

  2. Four possible outcomes

  3. Ratios depend on whether parents are homozygous or heterozygous
• Sex chromosomes


  One pair of chromosomes that determine gender, males have XY, females have XX
• Sex determination


  Egg cells always carry X chromosome

  2. Sperm cells can carry X or Y chromosome

  3. 50% chance of male or female offspring
• Gregor Mendel first explored genetic inheritance through experiments with pea plants in 1866
• Advancement of technology and the Human Genome Project has allowed genes to be mapped and their function understood
• Benefits of understanding genetics include identification of mutations, improved treatments, and advancements in fields like biofuels and agriculture
• Genetic engineering


  Desired gene is located and isolated

  2. Gene is replicated and placed into a vector

  3. Gene is inserted into a bacterium cell using the vector

  4. Successfully modified cells are selected
• Benefits of genetic engineering

  • Crops modified to improve yield, provide scarce nutrients, and help develop better medicines and vaccines

  Genetic testing can inform family planning and healthcare
• Risks of genetic engineering

  • Negative environmental impacts, long-term health impacts unknown, potential for 'designer babies'
• Allele


  A version of a gene (also known as variant)
• Amino acids


  Small molecules that make up a protein
• Biodiversity


  The variety of different organisms living in an ecosystem