BIOL 112 Study Guide - Midterm Guide: Lac Repressor, Operon, Wild Type

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24 Oct 2018

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BIOL 112 Full Course Notes

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The following three questions relate to the picture above. Cells have a lac operon and laci gene on the chromosome and a single plasmid with a lac operon and a laci gene. For each question, choose the best alternative that describes whether. Lacz is being made; if so at high level or basal levels and which operon encodes the. "normal function": the chromosomal lac operon and laci gene are wild type. The plasmid lac operon is missing only the laco region. The plasmid lac operon has a mutation that eliminates lacy but the rest of the operon and the laci gene are wild type. The plasmid lac operon is missing the lacz gene but the rest of the operon and laci gene are wild type. Cells have a malpq operon and malt gene on the chromosome and a single plasmid with a malpq operon and a malt gene.

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1.)A.)The lac operon is inducible by the presence of lactose. Loss-of-function mutations in the lacI gene, which encodes the lac repressor (pick all that apply):

A.)slow down the isomerization of lactose into allolactose
B.)decrease the amount of permease activity in the cell in the presence of lactose.
C.)prevent loss-of-function lacZ mutations from making the lac operon uninducible
D.)are recessive to wild type

B.)Mutations that eliminate the lacO operator site (pick all that apply):

A.)slow down the isomerization of lactose into allolactose
B.)decrease the amount of beta-galactosidase in the cell in the presence of lactose
C.)prevent lacS superrepressor mutations from making the lac operon uninducible
D.)are recessive to wild type

C.)Loss-of-function mutations in the lacZ gene, which encodes beta-galactosidase (pick all that apply):

A.)slow down the isomerization of lactose into allolactose
B.)decrease the amount of permease activity in the cell in the presence of lactose
C.)prevent lac repressor from binding the lacO operator site
D.)prevent IPTG from inducing the lac operon

D.)You are studying the Tory operon, which encodes the TorA and TorB genes, and is normally inducible by Torose. You find a mutation, m1, that causes the Tory operon to be uninducible. You examine the merodiploid (m1 TorA+ TorB-)/(+ ToryA- TorB+) and find that Tor A is uninducible and TorB is inducible. You conclude that:

A.)m1 acts in cis
B.)m1 acts in trans

ivorydog394

When (glucose, lactose) ___________ levels inside a bacterial cell are low, cyclicAMP levels are (high, low) __________. This is because metabolizes sugars (activate, inhibit) ___________ the enzyme adenylate cyclase, and (activate, inhibit) __________ the enzyme cAMP phosphodiesterase, causing cyclic AMP levels to rise. Consequently, the CAP protein is (Activated, inhibited, unaffected) ___________ by the cyclic AMP and binds to the lac promoter region, and the CAP protein acts like a sigma factor recruiting (DNA, RNA) ___________ polymerase to the promoter. This establishes condition that may lead to the (transcription, replication) __________ of the lac operon if (allolactose, glucose, lactose) _____________ is available to bind to (lac repressor, lacZ, lacY, lacA) _________ protein keeping this protein from binding to the (lacO, lacZ. lacY, lacA) ___________ gene.

yellowwasp623

please answer all the questions answering only one question is not helpful!
Question 1

0 / 1 pts

Which of the following E. coli strains with the lac genotypes will synthesize beta-galactosidase in the presence of lactose?

Note: Superscript wouldn't work in the answers, so for example, lacIs means lacI^s(superrepressor of lacI)

lacIâ lacPâ lacOâ lacZâ lacYâ

lacIs lacP+ lacO+ lacZ+ lacYâ / lacI+ lacP+ lacO+ lacZâ lacY+

lacIs lacPâ lacO+ lacZâ lacY+ / lacI+ lacP+ lacO+ lacZ+ lacY+

lacIâ lacPâ lacO+ lacZ+ lacY+

lacI+ lacP+ lacO+ lacZ+ lacY+

Question 2

0 / 1 pts

Some mutations in the trp 5' UTR region increase termination by the attenuator. An example of a mutation that may have this effect is a

Choose the best answer!

mutation that changes the bases in region 3 of the 5' UTR, such that they no longer pair with region 2 or 4.

deletion of the two tryptophan codons in the 5' UTR leader peptide.

deletion in region 2 in the 5' UTR that prevents it from pairing with region 3.

The second and third answers are correct.

The first, second, and third answers are correct.

IncorrectQuestion 3

0 / 1 pts

Several examples of antisense RNA regulating translation in bacterial cells have been discovered. If you wanted to design a construct to artificially control translation of a bacterial gene with antisense RNA, what type of sequences should the antisense RNA contain?

A sequence complementary to the operator of an operon.

A sequence complementary to a 5' UTR.

A sequence complementary to the Shine-Dalgarno site of the mRNA.

The first and second choices are correct.

The second and third choices are correct.

Question 4

0 / 1 pts

Which of the following correctly describes the function of microRNAs?

Choose the best answer.

MicroRNAs are encoded by genes in the genome of an organism.

MicroRNAs form mRNA which encodes a protein repressor for another gene.

MicroRNAs encode a mRNA that base pairs with itself, forming double stranded RNA.

MicroRNAs are cut into small pieces, then bound by the complex of proteins called RISC to repress the translation of other mRNAs in the cell.

The first and second answers are correct.

The first, third, and fourth answers are correct.

The third and fourth answers are correct.

whitemole409

BIOL 112 Study Guide - Midterm Guide: Lac Repressor, Operon, Wild Type

BIOL 112 Full Course Notes

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