genetics

• genotype?

  all the alleles that an organism carries on its chromosome
• phenotype?

  observable characteristics which are the result of the genotype and environmental factors
• most organisms are ...

  diploid
• what does diploid mean?

  two alleles for each gene they possess
• dominant allele?

  only one allele is required for it to be expressed in the phenotype
• what is one dominant allele called?

  heterozygous dominant
• what are two dominant alleles called?

  homozygous dominant
• recessive allele?

  characteristic only expressed if there is no dominant allele present
• what are two recessive alleles called?

  homozygous recessive
• what is a population?

  group of organisms of the same species occupying a space
• gene pool?

  number of alleles present in a population
• allele frequency?

  proportion of a certain allele in a gene pool
• what causes variations in genes for members of the same species?

  random fertilisation

  meiosis

  mutation

  environmental influences
• what does normal distribution look like?

  a bell curve - rises then falls
• what is the niche of a species?

  its role within the environment
• species which share the same niche ...

  compete with each other for survival

  better adapted species survive
• natural selection?

  better adapted species survive as they produce offspring and so their advantageous alleles are passed on
• the ... in genotypes and phenotypes increases the chances that a species will survive

  variation
• evolution via natural selection?

  there is many phenotypes in a population

  an environment will change and the selection pressure then changes

  some have an advantageous allele that will give them a selective advantage which allows them to survive and reproduce

  the advantageous allele passes to their offspring

  the frequency of alleles in a population changes which leads to evolution
• selection?

  the process by which individuals that are better adapted to the environment are more likely to survive, breed, and pass their advantageous alleles to their offspring
• what determines selection?

  the environment an organisms lives in
• three types of selection?

  directional, stabilising, disruptive
• example of directional selection?

  antibiotic resistance

  bacteria had a mutation, could grow and populate, frequency of the allele increases
• is stabilising selection due to environment changes?

  no, those closest to the mean are more likely to survive
• example of stabilising selection?

  new born babies closest to the mean survive, but those at the extremes are more likely to die
• disruptive selection?

  opposite of stabilising

  both the extremes are favoured over the mean

  animals adapted to survive without food due to increased body fat will survive longer than animals with the mean body weight
• gene?

  a sequence of bases on DNA that code for a protein which results in a characteristic
• codominant

  alleles that are both expressed in the phenotype, neither on recessive
• locus?

  the fixed position on a chromosome

  alleles found at the same locus on a pair
• homozygote?

  organism with the same allele eg. BB or bb
• heterozygote

  organism with two different alleles eg. Bb
• carrier?

  a person carrying an allele which isn't expressed in the phenotype but can be passed to offspring
• although individuals of the same species have the same ... they have different ... This causes ....

  genes

  alleles

  genetic variation
• what does genetic variation result in?

  evolution
• what does stabilising selection look like?

  gets thinner in the middle as selection pressures push it inwards
• what does directional selection look like?

  pushed towards one of the extremes by selection pressures
• what does disruptive selection look like?

  dips in the middle with two peaks

  the opposite of stabilising as the extremes are favoured
• what is speciation?

  the development of a new species
• how does speciation happen?

  when populations of a species become isolated and they cant interbreed anymore
• habitat?

  the place where an organism lives