Biology 1002B Chapter Notes - Chapter 14.1a-c: Regulon, Growth Medium, Cyclic Adenosine Monophosphate

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24 Feb 2017

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14. 1a the operon is a unit of transcription. For a typical metabolic process, several genes are involved, and they must be regulated in a coordinated fashion. A repressor is a regulatory protein that when bound to the dna, decreases the likelihood that genes will be transcribed. Typically, the proteins encoded by genes in the same operon catalyze steps in the same process. 14. 1b the lac operon for lactose metabolism is transcribed when an inducer. In the order of z-y-a, these genes are adjacent to one another on the chromosome, with the promoter and operator for the transcription upstream of z. note: collectively, this is called the lac operon. The lac operon is controlled by a repressor called the lac repressor. The lac repressor is encoded by the regulatory gene laci, which is nearby but separate from the lac operon and is synthesized in active form.

Related Questions

1 DNA sequences found in introns provide [A] amino acid sequence information.

[B] regulatory information.
[C] no known useful information.

[D] structure for the gene.
[E] alternative DNA splicing possibilities.

3. The TATA box is a(n)
[A] sequence close to the promoter region of many genes.
[B] square-shaped sequence.
[C] enhancer consensus sequence.
[D] activator sequence necessary for proper translation.
[E] None of the above

5. Regarding genes and gene expression, which of the following is not a difference between prokaryotes and eukaryotes
[A] Eukaryotic DNA does not contain a TATA box close to the initiation site as does prokaryotic DNA.

[B] In eukaryotes, RNA polymerase requires

'transcription factors'or initiation.

[C] Prokaryotic genes are often grouped together in

operons.

[D] In eukaryotes, the regulation of several genes at once requires common control elements in each of the genes.
[E] There is a diversity of eukaryotic polymerases that is reflected in the diversity of eukaryotic promoters.

10) In eukaryotic cells, a repressor

[A] is made of DNA.
[B] binds to the enhancer region to block transcription. [

C] is located both upstream and downstream from the promoter.
[D] binds to the operator to block RNA polymerase.

[E] binds to a silencer to reduce transcription rates.

Coordinated regulation of genes in eukaryotic cells [A] is the result of positioning the same regulatory sequence in front of each gene.
[B] results from all of those genes being under the control of one promoter.

[C] occurs because related genes all have the same

operons.
[D] occurs because enhancers cause DNA to bend.

1.) What type of control best describes the lac operon when it is regulated by allolactose? Explain the features of this type of regulation using the lac operon as an example.

2.) What is positive gene regulation?

a) when an activator protein binds to the operator of a gene to turn expression off

b) when a repressor protein binds to the operator of a gene to turn expression off

c) when an activator protein binds to the operator of a gene to turn expression on

d) when a repressor protein binds to the operator of a gene to turn expression on

e) when a protein binds to DNA to change gene expression

3.) In the lactose operon of E. coli, what is the function of each of the following genes or sites: a) regulator, b) operator, c) promoter, d) structural gene Z and e) structural gene Y?

a) regulator gene

b) operator

c) promoter

d) structural gene Z

e) structural gene Y

4.) In a negative, repressible regulatory mechanism, transcription of the structural gene(s) occurs in

a) the presence of the co-repressor, but not in its absence.

b) the absence of the co-repressor, but not in its presence.

c) the presence of the inducer, but not in its absence.

d) the absence of the inducer but not in its presence.

e) the absence or presence of the co-repressor.

What are answers and can you explain them to me?

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)

Biology 1002B Chapter Notes - Chapter 14.1a-c: Regulon, Growth Medium, Cyclic Adenosine Monophosphate

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