02 Mechanisms Variation Selection

Terminology you should know

heritability . dicer and RISC . silencing . transposons . retrovirusses . spontaneous and induced mutations . photolyase . transition and transversion . missense and nonsense mutations . eupolyploidy . facultative sexuality . monecious . diecious . hermaphroditic . proterandry . apomixis . gametophytic and sporophytic self-incompatibility


Concepts you should know, be able to explain, and remember

  • You can explain, which two factors are central for the generation of genetic variation

  • You can explain, what happens in a protein, when there is a missense mutation, what happens, when there is a nonsense mutation

  • You can explain, what is the evolutionary advantage of sexual propagation over asexual propagation

  • You can explain, what the principle of the different form of plant genders are

  • You can explain, why sporophytic SI is more stringent than gametophytic SI


To think about

  1. How many different gametes can be generated (ignoring crossing over) during meiosis for n=2, n=3, n=4, and n=5 chromosomes?
  2. White flower colour is a recessive trait. Can you explain why? You have a population of Viola elatior, where 16 % of individuals have white flowers. What percentage of the population is heterozygous for this trait? Remark: before you go to solve this problem, refresh your knowledge on the Hardy-Weinberg-Equation.
  3. Most flowers are hermaphroditic. Give two mechanisms (with a real example), how plants prevent self-fertilisation. 
  4. What happens, if a tomato with the genotype S1S2 is pollen donor for a tomato with genotype S2S3.
  5. What type of plants do you find in an androdiecious species.


To read and deepen