Genetic information and transfer

• genes


  where genetic information is stored
• genotype


  • the set of genes inherited
  • only fuzzy instructions, like a bake off technical recipe, not a blueprint.
  • same starting material, different outcomes
• phenotype


  individual characteristics and appearance
• genotype and phenotype relationship

  • genotype mostly determines phenotype
  • relationship is not always simple
  • there are other influences which can alter the observed effects
• other factors affecting phenotype

  • epigenetics
  • environment
  • randomness
• epigenetics

  • chemical modifications to genes that turn them on/off
  • heritable and passed on as cells divide
• environment

  • classic example is height - malnutrition stunts growth
  • in plants - day length and temperature cycles can affect flowering times
  • complex examples in human health e.g. heart disease, crohns disease
• randomness

  • during development some processes do not repeat exactly
  • cell - cell interactions may be subtly different
• how to study the effects of genetics?

  • take from very similar genetic backgrounds
  • use very similar environments
  • this will reduce the effects of phenotypic variation and is common in animal studies
  • use knockout or gene-edited animals to examine roles of genetic changes
• clones

  • with clones you can study the influence of environment
  • this is widely done with bacteria, yeast, and human cells
  • however animal clones are not always identical
• how to clone a mammal

  • take an egg cell and remove the genetic material
  • fuse the enucleated egg with a cell from the animal to be cloned, or transfer the nucleus from the donor cell
  • zap with an electrical pulse to activate the new hybrid cell
  • implant into surrogate mother and wait for delivery
• genetics of coat colour in cats

  • fur colour depends on a gene on the X chromosome
  • in female mammals, a random copy of X is inactivated
  • white patches are random action from another gene
• human cloning?

  • considered unethical and banned in most countries
  • gene editing is also prohibited
  • in the UK nuclear transfer can be used to avoid mitochondrial disease
• natural clones - identical twins

  • occur when a fertilised egg splits early during development
  • genetically identical and usually share a very similar environment
  • have been studied for many years to help disentangle genetics and environmental factors
  • difference increase with age in identical twins, as environment has more of an affect
• how can we use siblings and twins to estimate genetic contribution

  e.g. if a condition/phenotype is more commonly shared by identical twins than siblings, then likely strong genetic factors
• how do genes influence phenotypes

  • genes code for proteins
  • proteins act inside cells
  • cells interact with each other
  • organs and tissues are established
  • the organism assembles and grows
• genome


  complete set of genetic material within one chromosome set
• ecoli

  bp = 4,639,221

  gene number = 4,500
• budding yeast

  bp = 12,157,105

  gene number = 6604
• fruit fly

  bp = 143,726,002

  gene number = 13,000
• humans

  bp = 3,221,487,035

  gene number = 20,000