Lecture 26 Flashcards Preview

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Flashcards in Lecture 26 Deck (13):

Enzyme activity and fitness:

- An increasing amount of permease activity gives a increase of relative fitness
- An increasing amount of B-gal activity doesn't give an increase in relative fitness
- This is because permease allows more to enter the cell


Lactose utilization:

- Permease is responsible for lactose import through the cell membrane
- B-gal only acts on the lactose in the cell
- B-gal turns lactose into glucose for energy or galactose for energy
- Pearmease is the rate limiting step in the galactose pathway


Metabolic control theory:

- provides a link between enzyme kinetics and fitness
- Some steps have a greater impact on flux than others
- Theory expressed in terms of a model based on measurable kinetic parameters


Implications observed in bacteria:

- relative fitness difference between genotypes are often very small (b-gal in the presence of lactose)
- Relative fitness values vary between environments
- Selection may be stronger in extreme, atypical environments
- Pathway flu could be critical for fitness


Does natural selection act on phenotypes or individual genes?

- Phenotypes
- We should look at the whole individual instead of single genes


Speciation (reproductive isolation) leads to:

- Diversification of body plan
- There are very similar gene sets responsible for development in a variety of species


How does the diversification of body plan happen?

- Different gene sets in various species NO
- Same gene sets, with differences in regulation in various species
- Same gene sets with difference in coding region in various species


Notch gene:

- Developmental gene controlling almost every cell fate decision
- First cloned in drosophila
- But many species have the same gene with a similar aciton


Homeobox genes:

- Encode transcription factors that control the expression of other genes
- Found in two genomic locations in clusters, expressed along the organism in the same order
- Determine what body segments will become


Do species that differ in body plan differ in the sets of genes that specify their body plan?

- No!


Same gene sets - differences in regulation in various species

- Studied through in situ hybridisation


Tissue in situ hybridisation:

- Make a labelled probe that will bind to the mRNA of a specific gene
- Allows identification of the expression of certain genes across space and time
- The expression of genes can be laid over the body plan


Shifting patterns of hox gene expression across the arthropods:

- Changes in body plan are consistent with changes in pattern of gene expression, but this is just a correlation