Lecture 7 Flashcards
regions of the gene that are coded
Exons
Non coding regions of the gene
introns
alternate form of a gene
spelling
Allele
Pathogenicity
Property of causing disease
Genes that are absolutly required to cause disease. aka the genes that make an organism a pathogen
spelling
Pathogenicity genes
Genes that are associated with degree of virulence/agressivness on host. eg genes that help pathogens to spread faster, more capable of causing disease
spelling
Virulence genes/virulence factors
what happens when there is a disruption of pathogenicity genes
complete loss of disease/significant reduction in disease in plants
How is the variability in sexually reproducing organisms
all progeny (decendents) are variable
How is the variability in asexually reproducing pathogens
reduced degree/intensity and frequenct of variability among decendents. But the quantity is great meaning a low frequency of variablity could still be quite significant
What causes variability in plant pathogens
12 kinds & spelling
- Mutation
- sexual recombination
- Gene & genotype flow
- genetic drift
- selection
- life cycle
- pathogen fitness
- heterokaryosis
- parasexuality
- vegetative incompatibility
- heteroploidy
- sexual-like processes in bacteria (conjugation, transformation, transduction)
what do you call a loss of pathogen virulence in culture (spelling)
attenuation
Further classification based on what host the pathogen attacks
spelling
- ” special forms” (formae speciales)
- “Varirties”
Further classifications of special forms
spelling
- races
- pathotypes
further classifications of race & pathotypes
spelling
- isolates
each individual spore in an isolate
spelling
- biotype
How do plants defend themselves agasint pathogen attack
5 main ways & spelling
- non-host resistance
- basal defence (preformed structureal & chemical defense)
- induced structureal defence
- induced biochemical defence
- detoxification of plant pathogen toxins
- other mechanisms
What are the types of mutations
5 & spell them
- Signle nucleotide polymorphism (SNP)
- structural variations (insertion/deletion)
- frameshift mutation
- excision of transposable elements (TEs)
- complete loss of an allele/gene (rare)
Mutations
- sudden Heritable changes in the genetic material
- most mutations are recessive in nature there fore diploid/dikaryotic individuals can not expressed the mutations until they are brought together in a homozygous state
Mutation at a locus/allele that codes for an enzyme could produce a different allele that produces different enzyme
spelling
allozyme
Gene flow vs genotype flow
Gene flow:
- certain alleles (genes) move from one geographically separated population to another.
- lower in soil-borne fungi & nematodes
- Population 1 x popluation 2 -> making new population 3
Genotype flow:
- completel genotypes move into a new population. a feature of clonally/asxually reproducing pathogens
- Population 1 moving into population 2
increased population size & higher genetic diversity
Gene flow
lower genetic diversity but may increase diversity among populations
selection
Genotype flow example (like the name of the pathogen)
- rust
- mildew
Genetic drift
- random fluctuations in frequency of alleles in a population due to random sampling (in smaller populations)
What are the life cycles
3
- reproduction
- mating system
- outcrossing
Genotype diversity is higher than gene diversity
Asexual life cycle
gene/allelic diversity is higher than genotype diversity
both sexually and asexually
Pathogens that have greater diversity and produce more new genotypes have?
different mating systems and outcross
The ability for pathogen to reproduce and survive
pathogen fitness
How to quantify pathogen fitness
4 types, spelling
- Latent period (short / long)
- amount of disease/severity caused over space and time (agressivness)
- rate of spore production
- colony size
what happens when a population has lots of allelic/genetic load?
pathogen fitness selection favours individuals free of ‘excessive genetic load
what happens during pathogen survival and what is this called
- a change from avirulence to virulence
- “fitness penalty”
- fitness reduction will show up on both resistant and susceptible variety
what is 1-k
k = cost of fitness
fitness reduction of pathogen on susceptible varitey = 1-k
whats it called when hyphae of two different nucleus type fertilize / anastomosis
spelling & example
heterokaryosis
- Basidiomycetes fungi
when genetic recombination occurs within fungal heterokaryons
spelling. and what does it result in
- parasexuality
- results in fusion of two different haploid nuclei -> diploid nuclei and when the nucleus divides to revert to haploid nucleus individuals, crossover can occure and individuals formed can be very diverse
vegetative incompatibility
- hyphal anastomosis prohibition
- type of defence mechanism that protects individuals from harmful things that could reach them from other cells
abnormal number of chromosomes
heteroploidy
what are the sexual like processes in bacteria
3 main ones
- conjugation
- transformation
- transduction
two compatible bacteria come in contact with one another and a small portion of plasmid/chrmosome is transffered to the other through what?
whats this process called and what is being used to transfer & spelling
- conjugation
- conjugation bridge/ pilus
bacteria can undergo genetic transformation by absorbing and incorporating in their own cells genetic material relesed during rupture
transformation
bacterial virus, phage, transfering genetic material from one bacterium to another.
transduction
What are the other types of transduction and give example
- Horizontal & lateral transduction: when genetic info is transfered across kingdoms
- eg: agrobacterium tumefaciens
when two different strains are inoculated on the same plant, forming two or more variants.
this can happen can also occur in what
- genetic recombination in virus
- vector insects
