Biology 1002B Lecture Notes - Lecture 13: Lac Repressor, Lac Operon, Operon

33 views2 pages

cerisehornet51

24 Nov 2017

School

Western University

Department

Biology

Course

Biology 1002B

Professor

Tom Haffie Denis Maxwell

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Big green is a promoter , orange is a sd box, the blues ones are codons, red is clicker question stop codon, then the terminal sequence. Promoter is recognized and starts codon by the dna, termination sequence by the mrna and stops transcription. Promoter is the only signal in dna that are understood by the cell. Lactose metabliism is regulated by the lac operon in e. coli. A side reaction occurs and creates allolactose. The lac operon is inducible, it can turn on galactosidaease or not by lactose. Normally off but when lactose is there, there is a lot of galactosidaease. Laci- is always on lacz- is always off. Operons bring several genes under the control of one promoter laci, lacz and laca genes are all under control of single promoter. Mutation in laci gene destroys inducibility, which produces the repressor that binds to operator. Operators is another example of dna that is recognized in double stranded.

Related Questions

1) In the wildtype (the DNA sequence most commonly found in nature) lac operon, transcription is severely down-regulated. A mutation in lacI that causes an early stop codon in the sequence (called a lacI - strain) results in an operon that has high levels of transcription of the polycistronic m-RNA. What type of regulatory protein is the LacI protein (hint: we covered this type of protein in lecture)?

The Lac regulatory protein is called a repressor. (is this correct)

2) If a bacterium with a wildtype lac operon is grown in the presence of lactose, high levels of transcription result for a while, however, eventually transcription is again down-regulated. If, on the other hand, the sugar IPTG is present (instead of lactose), transcription levels are high and remain high. What function do IPTG and lactose share? How are they differently affected by the operon product? (need help with this question)

Lactose and IPTG affected by the operon are both inducers of the Lac-Operon. (is this correct)

3) What is âepigeneticsâ? What forms of gene regulation are usually involved in epigenetic control of a trait? Why do we have such a limited understanding of epigenetic processes? (need help with this question)

Epigenetics is the study of phenotype changes that do not change the DNA sequence. Genes can be turned on and off based on environment situations of past generations, (parents or even grandparents) were exposed. Examples of some environmental factors could be diet, stress, smoking, drinking alcohol, and diseases. Histone modification and methylation are usually involved in epigenetic control of a trait. (is this correct)

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

The TATA-binding protein (TBP) binds to the TATA box sequence in eukaryotic promoters. What is its function in transcriptional initiation?

It blocks access of RNA polymerase to the promoter, until removed by general transcription factors.

It is the subunit of prokaryotic RNA polymerase that is required to recognize promoters.

It modifies histones so nucleosomes can be removed from DNA for transcription.

It bends and partly unwinds DNA at a promoter.

The genetic code is said to be âdegenerateâ because

there are more codons than amino acids.

there are more amino acids than codons.

different organisms use different codons to encode the same amino acid.

some codons specify more than one amino acid.

Three general mechanisms appear to be responsible for the conversion of proto-oncogenes to oncogenes

overexpression, point mutations, deletions

inversions, translocations, methylation

familial, sporatic, phosphorylation

None of the above account for the conversion of proto-oncogenes into oncogenes

Transcriptional control of genes that acts by regulating the continuation of transcription is called

induction

attenuation

antitermination

negative inducible control

The genetic code is fairly consistent among all organisms. The term used to describe this consistency is

The F, G, and H loci are linked in the order written. There are 30 cM between F and G and 30 cM between G and H. If a plant Ff Gg Hh is testcrossed, what proportion of the progeny will be ff gg hh, assuming no interference?

DNA synthesis is always from 5â to 3â because

replication must be continuous

the strands are antiparallel

primers lack 3â to 5â exonuclease activity

In the ZZ-ZW sex-determination system, if an AaBb female was crossed to an individual of genotype Aa Bb, what is the probability of a female offspring with the two dominant traits given by alleles A and B? Assume A and B are dominant alleles.

Biology 1002B Lecture Notes - Lecture 13: Lac Repressor, Lac Operon, Operon

Document Summary

Get access

Related Documents

Biology 1002B Lecture Notes - Lecture 13: Lac Repressor, Lac Operon, Side Reaction

Biology 1002B Chapter Notes - Chapter 14: Catabolite Activator Protein, Cyclic Adenosine Monophosphate, Allolactose

Biology 1002B Lecture Notes - Lecture 14: Operon, Cyclic Adenosine Monophosphate, Dna Binding Site

Related Questions