translation and regulation of gene expression

Which statement(s) about inducible operons is/are correct? -In an inducible operon, the repressor is synthesized in an active form. -Inducible enzymes generally function in synthetic pathways that produce end products from raw materials. -In an inducible operon, an inducer inactivates the repressor

-In an inducible operon, the repressor is synthesized in an active form -In an inducible operon, an inducer inactivates the repressor

How are genes coordinately controlled in eukaryotic cells?

Coordinately controlled genes in eukaryotic cells are activated by the same chemical signals and share a set of control elements

RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such variability in RNA polymerase?

It might allow the polymerase to recognize different promoters under certain environmental conditions

During splicing, which molecular component of the spliceosome catalyzes the excision reaction?

RNA

repressor

a protein that inhibits gene transcription. In prokaryotes, this protein binds to the DNA in or near the promoter

operon

a stretch of DNA consisting of an operator, a promoter, and genes for a related set of proteins usually making up an entire metabolic pathway

Amino acids are attached to tRNA by enzymes called

aminoacyl-tRNA synthetase

miRNAs can control gene expression by what action?

binding to mRNAs and degrading them or blocking their translation

regulatory gene

codes for a protein,such a repressor, that controls the transcription of another gene or group of genes

DNA methylation is a mechanism used by eukaryotes to do what?

inactivate genes

A eukaryotic transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that

many noncoding stretches of nucleotides are present in eukaryotic DNA

Negative control

-When lactose is absent, the repressor protein is active, and transcription is turned off. -When lactose is present, the repressor protein is inactivated, and transcription is turned on.

tRNA has_________and contains______

-amino acids covalently attached -contains an anticodon

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of ATP, GTP, and UTP. How many artificial mRNA 3 nucleotide codons would be possible?

27

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?

RNA polymerase II

It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?

Short-lived proteins enable the cells to control their activities precisely and efficiently

_____ of translation happens when the ribosome hits a stop codon on the mRNA

Termination

Positive control

When glucose is absent, another regulatory protein (CAP) binds to the promoter of the lac operon, increasing the rate of transcription if lactose is present

You are given an experimental problem involving control of a gene's expression in the embryo of a particular species. One of your first questions is whether the gene's expression is controlled at the level of transcription or translation. Which of the following might best give you an answer?

You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same

What does a mutagen cause?

a change in the sequence of DNA

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of two nucleotides

Inducer

a specific small molecule that binds to a bacterial regulatory protein and changes its shape so that it cannot bind to an operator, this switching an operon on.

Which of the following nucleotide triplets best represents a codon?

a triplet in the same reading frame as an upstream AUG

When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate?

an assembled ribosome with a polypeptide attached to the tRNA in the P site

In eukaryotes, general transcription factors

bind to other proteins or to a sequence element within the promoter called the TATA box

Steroid hormones produce their effects in cells by

binding to intracellular receptors and promoting transcription of specific genes

the _________are arranged sequentially after the promoter

genes of an operon

In humans, the hormone testosterone enters cells and binds to specific proteins, which in turn bind to specific sites on the cells' DNA. These proteins probably act to do what?

help RNA polymerase transcribe certain genes

_____of translation always happens at the start codon of the mRNA

initiation

When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?

methylation and phosphorylation of histone tails

regulatory proteins bind to the _____to control expression of the operon

operator

Transcription factors in eukaryotes usually have DNA binding domains as well as other domains that are also specific for binding. In general, which of the following would you expect many of them to be able to bind?

other transcription factors

promoter

specific nucleotide sequence in DNA that binds RNA polymerase positioning it to start transcribing RNA at the appropriate place

the RNA that has an amino acid attached to it, and binds to the codon on the mRNA is called

tRNA

the process performed by the ribosome of reading mRNA and synthesizing a protein is called

trasnlation