Final Exam

Question 1

What are the 4 components in the role of DNA?

Answer 1

Replication
Transcription
Translation
DNA repair

Question 2

what does the sigma factor do?

Answer 2

directs the RNA polymerase core enzyme to a promotor

Question 3

what is rho-dependent transcription?

Answer 3

rho protein follows RNA polymerase and removes it when it reaches the termination sequence

Question 4

what is rho-independent transcription?

Answer 4

hair-pin loop forms in RNA which causes RNA polymerase to remove itself

Question 5

Brief explanation of translation in bacteria

Answer 5

small ribosomal subunit and Shine-Delgarno sequence align machinery to correct location. Multiple Shine-Delgarno sequences allows bacteria to be polycistronic

Question 6

two environmental factors that effect regulation

Answer 6

• changes in nutrients and availability

- changes in competition

Question 7

what are two constitutive processes in the cell (housekeeping genes)

Answer 7

TCA cycle and ATP synthases

Question 8

when can gene expression be controlled?

Answer 8

transcription, translation, post-translation

Question 9

what are the 4 types of covalent modification?

Answer 9

alters enzyme conformation:

• phosphorylation
• acetylation
• methylation
• glycosylation

Question 10

describe allosteric inhibition

Answer 10

the final product of a pathway often inhibits the activity of the enzyme in the first steps of the pathway. the product may bind to the enzyme and change its conformation so that it can no longer bind to the active site. inhibition or activation is possible through this process

Question 11

what is an operon?

Answer 11

a transcriptional unit with a series of structural genes and regulatory elements

Question 12

parts of the lac operon

Answer 12

• lacI: repressor
• promotor
• operator
• lacZ: beta-galactosidase
• lacY: permease
• lacA: transacetylase

Question 13

allosteric in positive control

Answer 13

activates mRNA synthesis

Question 14

allosteric in negative control

Answer 14

prevents mRNA synthesis

Question 15

what is attenuation

Answer 15

interruption of transcription after initiation but before termination

Question 16

explain attenuation

Answer 16

• interaction between translation and transcription
• if ribosome quickly follows RNA polymerase, hairpin loops are formed in the leader sequence and the polymerase detaches
• “stalling out” of ribosome (ex. not enough amino acid in tRNA)
• does not occur in eukaryotes

Question 17

what is quorum sensing?

Answer 17

chemical signalling system that allows microbes to communicate with each other. it is regulated by population density

Question 18

what are the two example organisms in quorum sensing

Answer 18

Hawaiian bobtail squid that has vibrio fisheri in its light organ

Question 19

how do vibrio fisheri produce light?

Answer 19

• when in high density they produce N-acyl-homoserine lactone (AHL) which stimulates luminescence
• luxI protein catalyzes AHL synthesis
• luxR (regulator transcriptional activator) interacts with AHL in high concentration
• binds the lux box DNA regulatory site
• leads to transcription of luciferase protein genes and luxI, which creates positive feedback loop forming more AHL