Lecture 26

Question 1

Enzyme activity and fitness:

Answer 1

• 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

Question 2

Lactose utilization:

Answer 2

• 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

Question 3

Metabolic control theory:

Answer 3

• 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

Question 4

Implications observed in bacteria:

Answer 4

• 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

Question 5

Does natural selection act on phenotypes or individual genes?

Answer 5

• Phenotypes

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

Question 6

Speciation (reproductive isolation) leads to:

Answer 6

• Diversification of body plan

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

Question 7

How does the diversification of body plan happen?

Answer 7

• 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

Question 8

Notch gene:

Answer 8

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

Question 9

Homeobox genes:

Answer 9

• 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

Question 10

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

Answer 10

• No!

Question 11

Same gene sets - differences in regulation in various species

Answer 11

• Studied through in situ hybridisation

Question 12

Tissue in situ hybridisation:

Answer 12

• 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

Question 13

Shifting patterns of hox gene expression across the arthropods:

Answer 13

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