IB 432 LAST EXAM

What are intraspecies interactions

• potent influences of the social environment (others behavior) on gene expression

• beneficial microbiome, pathogenic microbes, parasites

• these organisms interact very intimately with host and thus they may exert powerful effects on host phenotypes and genomes

What is the holobiont theory

• assemblages of different species that form ecological units

  • what we think is one individual is a collection of organisms

• microbiota can play an essential role in homeostasis and survival

what is the hologenome

• consist of the genomes of many

• phenotype you see is the result of the collective genomes of many players

• could even influence the evolution of each others genomes

what is the extended phenotype

• an extension of the ‘selfish gene’ idea

• idea that the effect of a gene extends beyond the phenotype of the organism —> whose genome affects phenotypes of others and its surrounding

what is host manipulation

• type of extended phenotype

• when a parasite or pathogen changes the phenotype of its host in a way that benefits the parasite/pathogen but DOES NOT benefit the host

• the genes of the parasite/pathogen have been selected to ‘reach into’ the host genome and change host gene activity to their benefit

• IE) mice with toxoplasmosis

How do parasites accomplish host manipulation

• changes in sensory perception

• changes in brain function

• changes in development

• On a molecular level, the transcriptome, due to its dynamic nature, is an easy target

what are differences in female wasp

• behavioral differences

  • care taking or reproduction

  • aggression or submission

• Physiological differences

  • cuticular hydrocarbons

  • facial marking

  • fat stores

  • ovary development

  • larval development

  • longevity

• Wasp females have flexible castes and can switch from queen to worker or worker to queen, even as adults

PARASITE TRIES TO TAKE ADV OF THIS PLASTICITY

what happens when wasp is infected

would be workers shift their behavior to the wrong caste

• smaller size, no nest work, long lived

• a combo of gyne and worker wasp

What does figure show (wasp paper)

• heatmap showing differential expression patterns for each group

  • red=downreg

  • green=upreg

  • relative to the mean of each gene

• each group has a unique pattern

• stylopized show a gene expression pattern more similar to gyne caste

What does this figure show (wasp paper)

Venn diagram of DETs(dif expressed transcripts) in pairwise comparison groups

• largest gene expression differences based social caste (worker vs gyne)

• Candidate genes identifies = 14 DETs in worker vs. stylopized were related to caste differences

What does this figure show (wasp paper)

• comparison of the resd count ratios for the 14 overlapping DETs between S/W and G/W

• high correlation

• shows similarity between stylopized and gyne gene expression

what does this figure show (wasp paper)

• compares the results of qRT-PCR and RNA seq for defensin and IRP30

• suggest the immune system of wasp are stimulated during stylopization

what are the conclusions of the wasp paper

• paracites can manipulate host behavior through changes in gene expression related to host phenotypic plasticity

• Hijacking of plasticity in gene expression can be potential mechanism for changing host phenotype to parasite adv

• the host parasite system can be used to look at the molecular basis of complex phenotypes

• used this model to gain more info on social genes of other similar organism

• example of how an extended phenotype can be reg by multiple organisms

what is molecular epigenetic

stable potentially long term changes in the activity of a gene (and its associated phenotype) that do not require a change in DNA sequence

• can be inherited across cell divisions

• can also be reversible

• BUT some may persist through meiosis and even be inherited across generations

What is gene expression related to

gene expression is related to the 3D structure of DNA

• epigenetic marks such as methylation can affect this structure and thus gene expression

• closed DNA = no transcription

• open DNA = transcription factors can bind and induce gene expression

wha the big deal about epigenetics

• through epigenetics the environment leaves a stamp on the genome —> genomic memory

• experience can have long lasting impacts on how the genome functions for the rest of a lifetime

• inheritance of environmentally induced traits

what are the two major epigenetic marks

• chemical modification to DNA that affect chromatin structure

1) DNA methylation

2) Histone modifications

what is DNA methylation

addition of methyl group to dna usually at C bases

makes DNA less expressed

• more tightly bound to chromatin and block access of transcription factors

accomplished by DNA methyltransferase

what are histone modifications

additions of acetly or methyl groups to histones

affect how tightly wound NDA is around histones and how accessible it is to transcription

accomplished by histone acetyl transferase and histone deactylases

Relationship with epigenetic and behavior

• first human studies on epigenetic mech related to human health

  • environmental influence in ur life can change ur risk of cancer

• could environmental factors such as social environment also act on genome through epigenetic