T6- Inheritance, variation and evolution

• allele


  different versions of the same gene
• genotype


  the genetic constitution of an individual organism
• phenotype


  the set of observable characteristics of an individual, resulting from the interaction of the genotype with the environment
• heterozygous


  having two different alleles of a particular gene or genes
• homozygous


  having 2 identical alleles of a particular gene
• dominant alleles 


  effectively overrules the other allele

  always represented by capital letters
• recessive alleles


  has to have two copies of the allele to show its effect

  always represented by a lower case letter
• mutation


  a change in the sequence of a base

  they occur continuously and spontaneously
• types of mutation: insertion


  new base inserted where it should not be

  knock on effect later on
• types of mutation: deletion


  random base removed from the sequence

  knock on effect later on
• types of mutation: substitution


  random base changed to another
• XX is the female chromosome
• XY is the male chromosome
• Darwin

  Came up with the theory of evolution

  people disagreed with him because: lack of evidence (small fossil records then); it opposed creation in the bible and people did not know about genes
• Lamarck

  did work on evolution

  said that animals acquire characteristics based on their environment eg giraffes have a long neck because they stretch it every time they reach for leaves
• Linnaeus

  grouped things based on their characteristics and structure

  created the Linnaean system of classification
• Linnean system

  Kingdom

  Phylum

  Class

  Order

  Family

  Genus

  Species
• Woese- 3 domain system (1990)


  Three largest categories of classification, above the kingdoms:

  Archaea - extremophile prokaryotes

  Bacteria - true bacteria eg E.coli

  Eukaryotes - plants, animals, fungi and protists
• Wallace

  He also came up with the idea of natural selection, then worked together with Darwin

  his key idea: warning colours used by species to deter predators
• Mendel 


  Created the foundations for modern genetics

  worked on pea plants and reached three conclusions:

  characteristics are determined by units

  they can be dominant or recessive

  passed on unchanged

  His units were later found to be genes
• speciation

  the development of a new species through isolation and natural selection
• species

  a group of similar organisms that reproduce together to create fertile offspring
• survival of the fittest

  organisms with the best suited characteristics are most likely to survive and breed
• 5 reasons for extinction

  New disease

  new predator

  catastrophic event

  cannot compete for food

  rapid environment change
• cystic fibrosis 


  a disorder of the cell membranes - affects the digestive and respiratory systems as thick mucus blocks ducts in the air passages and the pancreas

  caused by a recessive allele
• Polydactyly 


  having extra fingers or toes

  caused by a dominant allele
• embryonic screening 


  analysing the genes of a cell from an embryo to see if there is any 'bad' alleles presents