Bio 181 Exam 3

In the hierarchy of levels of gene regulation, in what order do the following levels of regulation take place? (1) post-translational modification (2) RNA processing (3) transcription (4) chromatin remodeling

(4)-(3)-(2)-(1)

operon

A group of proteins, whose functions are often related, whose genes are situated together on the same stretch of DNA.

Catabolite Activator Protein

A positive regulator of gene expression. This trans-acting factor binds to the promoter of operons in the presence of cAMP to increase the affinity of that promoter region to RNA polymerase - resulting in an increase in transcription of downstream genes.

Repressor

A protein that binds to DNA or RNA that inhibits the expression of one or more genes by binding to the operator.

Transcription factor

A protein that controls the rate of transcription of genetic information from DNA to mRNA by binding to a specific DNA sequence.

Activator

A protein transcription factor that increases gene transcription of a gene or set of genes.

Operator

A segment of DNA to which a transcription factor binds to regulate gene expression by repressing it.

trp operon

An example of a repressible operon. If tryptophan is absent, this operon expresses genes responsible for synthesizing more tryptophan.

lac operon

An operon necessary for the transport and breakdown of lactose in E. Coli and other bacteria.

It is necessary for the gene that codes for the repressor of lac operon to be physically near the structural genes on the same stretch of DNA.

False

Which of the following genotypes produces functional lactose permease constitutively?

I- P+ O+ Z- Y+

A single gene can produce different proteins.

True

For the lactose operon, the CRP-cAMP is a(n):

activator

Which of the following processes produce different proteins in different cells from the same primary transcript?

alternative splicing

In eukaryotes gene regulation can occur

at the transcriptional level at the transcriptional level at the transcriptional level

In the lactose operon of E. coli, the lacP- mutation:

bound to the regulatory region of the operon.

Methylation, acetylation, and other histone modifications are important because they are associated with:

chromatin remodeling and affect gene transcription.

Gene regulation by means of epigenetic mechanisms is useful to the organism because it:

does not require new mutations. can quickly be reversed. can respond rapidly to environmental change. can differ between the sexes.

Chemical modifications of bases, changes to histones, and alterations in chromatin structure that regulate gene expression are said to be:

epigenetic

The human body contains approximately 200 major cell types. They look and function differently from one another because each:

expresses a different set of genes and/or different variations on the same genes.

The CRP-cAMP complex binds the lactose operon when:

glucose levels are low and cAMP levels are high.

Sex-specific silencing of gene expression is known as:

imprinting

Positive and negative transcriptional regulation differ in that:

in positive regulation, the binding of a regulatory protein to the DNA is necessary for transcription to occur; in negative regulation, such binding prevents transcription.

For the lactose operon, lactose is a(n):

inducer

A mutant strain of E. coli is found that produces both β-galactosidase and permease constitutively. What are the MOST likely mutations in this strain? (Select all that apply: hint** There are two correct answers.)

lacI- lacOc

You identify a mutation affecting the lac operon and find the following: lacZ is expressed whether lactose is present or not. lacI is expressed normally. What could be WRONG in this mutant?

lacO (operator) is mutated such that the repressor protein, I, will not bind

In a normally functioning 'wild type' bacteria, The lacZ and lacY genes are transcribed when:

lactose is present and glucose levels are low.

In the lactose operon of E. coli, the product of the lacI gene is a(n) _____ of transcription.

negative regulator

In the lactose operon of E. coli, the CRP-cAMP complex is a(n) _____ of transcription.

positive regulator

Gene regulation in prokaryotes can occur

primarily at the transcriptional level.

An operon is a

region of DNA consisting of the promoter, the operator, and coding sequences for structural proteins.

In E. coli, an isomer of lactose binds with the lactose operon:

repressor, preventing it from binding to the operator. This allows the lacZ and lacY genes to be transcribed.

In order to analyze how different components of the lac operon work, scientists created special strains of E. coli, called partial diploids. A partial diploid has one full copy of the lac operon in the bacterial chromosome plus another copy of the lac operon in a plasmid. Hence, for the lac operon (and only the lac operon) the bacterial cell is a diploid. Below is one possible genotype of a partial diploid. The genotype written to the left of the slash (/) is that of the lac operon in the bacterial chromosome, and the genotype written to the right of the slash is that of the lac operon in the plasmid. I+ P+ O+ Z-/I+ P+ O+ Z+ For the partial diploid genotype shown here, determine whether functional β-galactosidase is synthesized in the absence and in the presence of lactose (and the accompanying allolactose that is the actual inducer).

β -galactosidase is produced when lactose is present but is not produced when lactose is absent.

In order to analyze how different components of the lac operon work, scientists created special strains of E. coli, called partial diploids. A partial diploid has one full copy of the lac operon in the bacterial chromosome plus another copy of the lac operon in a plasmid. Hence, for the lac operon (and only the lac operon) the bacterial cell is a diploid. Below is one possible genotype of a partial diploid. The genotype written to the left of the slash (/) is that of the lac operon in the bacterial chromosome, and the genotype written to the right of the slash is that of the lac operon in the plasmid. I+ P- O+ Z+/ I- P+ O+ Z- For the partial diploid genotype shown here, determine whether functional β-galactosidase is synthesized in the absence and in the presence of lactose (and the accompanying allolactose that is the actual inducer).

β-galactosidase is not produced whether lactose is present or absent.

In order to analyze how different components of the lac operon work, scientists created special strains of E. coli, called partial diploids. A partial diploid has one full copy of the lac operon in the bacterial chromosome plus another copy of the lac operon in a plasmid. Hence, for the lac operon (and only the lac operon) the bacterial cell is a diploid. Below is one possible genotype of a partial diploid. The genotype written to the left of the slash (/) is that of the lac operon in the bacterial chromosome, and the genotype written to the right of the slash is that of the lac operon in the plasmid. I+ P+ Oc Z+/ I- P- O+ Z- For the partial diploid genotype shown here, determine whether functional β-galactosidase is synthesized in the absence and in the presence of lactose (and the accompanying allolactose that is the actual inducer).

β-galactosidase is produced whether lactose is present or absent.