cell final Flashcards

In the process of transcription, _____

a) DNA is replicated

b) RNA is synthesized

c) proteins are synthesized

d) mRNA attaches to ribosomes

Which of the statements below is false?

a) the genetic code is overlapping

b) the genetic code is nearly universal

c) redundant codons specify the same amino acids

d) the genetic code is triplet

Transcription is eukaryotes requires which of the following in addition to RNA polymerase?

a) start and stop codons

b) ribosomes and tRNA

c) several transcription factors

d) aminoacyl-tRNA synthetase

The completed assembly of transcriptions factors and RNA polymerase II bound to a promoter is called

a) the TATA box complex

b) the recognition site for ribosomal binding

c) the transcription initiation complex

d) the template strand

Alternative RNA splicing_______.

a) is a mechanism for increasing the rate of translation

b) can allow the production of proteins of different sizes and function form a single mRNA

c) can allow the production of similar proteins from different RNAs

d) increases the rate of transcription

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following would you expect her to find?

a) the mRNA is quickly converted into a ribosomal subunit

b) the cell adds a new poly-A tail to the mRNA

c) the mRNA attaches to a ribosome and is translated, but more slowly

d) the molecule is digested by enzymes because it is not protected at the 5' end

Which one of the following statements about RNA splicing is false?

a) introns are removed before mRNA leaves the nucleus

b) ribozymes are an RNA component of the spliceosome that catalyze the splicing reaction.

c) RNA splicing can be catalyzed by tRNA in the spliceosome

d) alternative splicing results in one gene encoding multiple different proteins

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the ______.

a) binding of ribosomes to mRNA

b) binding of the anticodon to small subunit of the robosome

c) attachment of amino acids to rRNAs

d) binding of the anticodon to the codon and the attachment of amino acids to tRNAs

There are sixty-one mRNA codons that specify an amino acid, but only forty-five tRNAs. This is best explained by the fact that _____.

a) some tRNAs have anticodons that recognize four or more different codons

b) the rules for base pairing between the third base of a codon and tRNA are flexible

c) many codons are never used, so the tRNAs that recognize them are dispensable

d) the DNA codes for all sixty-one tRNAs, but some are then destroyed

Which of the following is the first event to take place in translation in eukaryotes

a) base pairing of activated methionine-tRNA to AUG of the messenger RNA

b) binding of the larger ribosomal subunit to smaller ribosomal subunits

c) covalent bonding between the first two amino acids

d) the small subunit of the ribosome recognizes and binds to the mRNA

Translation requires______.

a) mRNA, tRNA, DNA and rRNA

b) mRNA, DNA, and rRNA

c) mRNA, tRNA, and rRNA

d) mRNA, tRNA, and DNA

Once a peptide has been formed between the amino acids attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next?

a) translocation

b) reading of the next codon of mRNA

c) initiation

d) the codon-anticodon hydrogen bonds holding the tRNA in the A site are broken

what is the correct order for the steps during translation elongation?

a) codon recognition, translocation, peptide bond formation

b) transcription, mRNA, formation, signal peptide translocation

c) splicing, codon recognition, peptide bond formation

d) codon recognition, peptide bond formation, translocation

how does termination of translation take place?

a) the end of the mRNA molecule is reached

b) a stop codon is reached

c) the 5' cap is reached

d) the pol-A tail is reached

A signal peptide _______.

a) directs an mRNA molecule into the eisternal space of the ER

b) terminated translation of messenger RNA

c) helps target a protein to the ER

d) signals the initiation of transcription

Which of the following statements is true about protein synthesis in prokaryotes?

a) extensive RNA processing is required before prokaryotic

b) Translation can begin while transcription is still in progress

c) Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles

d) unlike eukaryotes, prokaryotes require no initiation or elongation factors

a ribozyme is ______.

a) a catalyst that uses RNA as a substrate

b) an RNA with catalytic activity

c) an enzyme that catalyzes that association between the large and small ribosomal subunits

d) an exzyme that synthesizes RNA as part of the transcription process

Which of the following, when taken up by a cell, binds to a repressor so that the repressor no longer binds to the operator?

a) inducer

b) promoter

c) repressor

d)corepressor

In bacteria, if lactose is available and glucose is scarce then:

a) cAMP levels will be high, CAP will bind tightly to the lac promoter, and the lactos structural genes will be expressed at a high level

b) cAMP levels will be low, CAP will not bind to the lac promoter, and the lactose structural genes will not be expressed

c) cAMP levels will be low, CAP will not bind to the lac promoter, and the lactose structural genes will be expressed at a low level.

d) cAMP levels will be high, CAP will not bind to the lac promoter, and the lactose structural genes will be expressed at a high level

In bacteria, if lactose and glucose are both available at high concentrations then:

a) cAMP levels will be high, CAP will bind tightly to the lac promoter, and the lactose structural genes will be expressed at a high level.

b) cAMP levels will be low, CAP will not bind to the lac promoter, and the lactose structural genes will not be expressed.

c) cAmP levels will be low, CAP will not bind to the lac promoter, and the lactose structural genes will be expressed at a low level

d) cAMP levels will be high, CAP will not bind to the lac promoter, and the lactose structural genes will be expressed at a high level

the trp repressor blocks transcription of the trp operon when the repressor______.

a) binds to the inducer

b) binds to tryptophan

c) is not bound to tryptophan

d) is not bound to the operator

Imagine that you've isolated a yeast mutant that contains histones resistant to acetylation. What phenotype do you predict for this mutant

a) the mutant will grow rapidly

b) the mutant will require galactose for growth

c) the mutant will show low levels of gen expression

d) the mutant will show high levels of gene expression

the reason for differences in the sets of proteins expressed in the nerve and a pancreatic cell of the same individual is the nerve and pancreatic cells contain different _______.

a) genes

b) regulatory sequences

c) sets of regulatory proteins

d) promoters

Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?

a) environmental signals enter the cell and bind directly to promoters

b) the genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time

c) the genes are organized into a large operon, allowing them to be coordinately controlled as a single unit

d) a single repressor is able to turn off several related genes

In an experiment, you are able to increase the level of acetylation of histone tails. Which of the following results would you most likely see?

a) increased chromatin condensation

b) decreased chromatin condensation

c) decreased binding of transcription factors

d) inactivation of the selected genes

which of the following best describes siRNA?

a) a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA

b) a single-stranded RNA that can, where it has internal complementary base pairs, fold into cloverleaf patterns

c) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor

d) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits

Which method is utilized by eukaryotes to control their gene expression that is not used in bacteria?

a) control of chromatin remodeling

b) control of RNA splicing

c) transcriptional control

d) control of both RNA splicing and chromatin remodeling

Epigenetic changes

a) lead to changes in the genotype of an organism

b) are never inherited

c) are caused by external or enviormental factors that switch genes on or off

d) involve changes in the nucleotide sequence of an organism

The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called_______.

a) RNA interference

b) RNA obstruciton

c) RNA blocking

d) RNA disposal

+

Mechanisms that regulate eukaryotic gen expression include all of the following except:

a) mRNA degradation

b) protein degradation

c) initiation of transcription

d) DNA repleciation

e) RNA processing

sf) rate of translation

A principal problem with inserting an unmodified mammalian gene into a plasmid and then getting that gene expressed in bacteria is that _______.

a) prokaryotes use a different genetic code from that of eukaryotes

b) bacteria translate only mRNAs that have multiple messages

c) bacteria may not provide that required post-translational modifications to make functional mammalian protein

d) bacterial RNA polymerase cannot make RNA complementary to mammalian DNA

Sequencing an entire genome, such as that of Drosphila melanogaster, a model organism, is most important because ________.

a) it allows researchers to use the sequence to build a "better" fruit fly, which is resistant to disease

b) it allows research on a group of organisms we do not usually care much about

c) a sequence that is found to have a particular function in the fruit fly is likely to have a closely related function in vertebrates

d) a sequence that is found to have no introns in the fruit fly genome is likely to have acquired the introns from higher organisms

Why is it so important to be able to amplify DNA fragments when studying genes?

a) before amplification, DNA fragments are likely to bind to RNA and no longer be able to be analyzed

b) a gene may represent only a millionth of the cells DNA

c) restriction enzymes (endonucleases) cut DNA into fragments that are too small

d) a clone requires multiple copies of each gene per clone

The reason for using Taq polymerase for PCR is that ______

a) it is heat stable and can withstand the heating step of PCR

b) only minute amounts are needed for each cycle of PCR

c) it binds more readily than other polymerases to the primers

d) it has regions that are complementary to the primers

What is the most logical sequence of steps for making a recombinant DNA molecule?

I. Transform bacteria with a recombinant DNA molecule

II. Cut the plasmid DNA using restriction enzymes (endonucleases).

III. Extract plasmid DNA from bacterial cells

IV. Use ligase to seal plasmid DNA to nonplasmid DNA

a) II, III, IV, I

b) III, II, IV, I

c) III, IV, I, II

d) IV, I, II, III

Which of the following sequences is most likely to be cut by a restriction enzyme?

a) AATTCT

TTAAGA

b) AATATT

TTATAA

c) AAAATT

TTTTAA

d) ACTACT

TGATGA

Which of the following is the correct order for once cycle of polymerase chain reaction (PCR)?

a) denature DNA; add fresh enzyme; anneal primers; add dNTPs; extend primers

b) anneal primers; denature DNA;; extend primers

c) Extend primers; anneal primers; denature DNA

d) Denature DNA; anneal primers; extend primers

Which of the following is required to make complementary DNA (cDNA) from RNA?

a) restriction enzymes ( endonucleases)

b) gene cloning

c) DNA ligase

d) reverse transcriptase

RNA sequencing has made a huge impact on genomic studies because it ______.

a) can be used to eliminate the function of any gene in the genome

b) can be used to introduce entire genomes into bacterial cells

c) provides the identification and quantification of all the transcripts (mRNA and non-coding RNA) in a cell at a given moment of time

d) allow physical maps of the genome to be assembled in a very short time

RNAi methodology uses double-stranded pieces of RNA to trigger degradation of a specific mRNA or inhibit its translation. For which of the following might this technique be useful?

a) to decrease the production form a harmful mutated gene

b) to destoy an unwanted allele in a homozygous individual

c) to form a knockout organism that will not pass the delected sequence to its progeny

d) to raise the concentration of a desired protein

What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids?

a) the primary structure of the protein would be changed

b) the tertiary structure of the protein might be changed

c) the biological activity or function of the protein might be altered

d) only A and C are correct

e) A, B, and C are correct

What three modification are made to mRNA before it leaves the nucleus?

What sequencing technology has allowed scientist to perform massively parallel sequencing reactions, resulting in the reduced cost and increased speed of sequencing?

What protein and protein complex are involved in RNA interference?