Biology 012 Final Exam

Biology 012 Final Exam Biology 012 Lecture Flash Cards
  
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RNA viruses require their own supply of certain enzymes because
 
host cells lack enzymes that can replicate the viral genome
Viral DNA makes mRNA by the process of _____.
 
transcription
How do prions, which are misfolded proteins, infect organisms
 
Prions enter brain cells and cause normal forms of the protein to refold into the prion form
The functioning of enhancers is an example of
 
the stimulation of translation by initiation factors
miRNAs can control gene expression by what action?
 
binding to mRNAs and degrading them or blocking their translation
cDNA is synthesized from what molecule using an enzyme known as what?
 
mRNA ... reverse transcriptase
A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have
 
T4 protein and T4 DNA
Which of the following statements about the DNA in one of your brain cells is true?
 
It is the same as the DNA in one of your heart cells
Muscle cells differ from nerve cells mainly because they
 
express different genes
Which of the following statements best defines the term operon?
 
An operon is a region of DNA that codes for a series of functionally related genes under the control of the same promoter
What molecule binds to promoters in bacteria and transcribes the coding regions of the genes?
 
RNA polymerase
What is allosteric regulation?
 
In allosteric regulation, a small molecule binds to a large protein and causes it to change its shape and activity.
Under which conditions are the lac structural genes expressed most efficiently?
 
No glucose, high lactose
What happens to the expression of the lacI gene if lactose is not available in the cell?
 
There is no change—the lacI gene is constitutively expressed.
What is the function of the lacZ gene?
 
This gene encodes an enzyme, b-galactosidase, which cleaves lactose into glucose and galactose.
Which of the following enzymes converts ATP to cAMP
 
Adenylyl cyclase
True or false? The mechanism by which glucose inhibits expression of the lac structural genes is known as catabolite stimulation, whereas the mechanism by which lactose stimulates expression of the lac structural genes is known as allosteric regulation.
 
False
What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?
 
continuous transcription of the operon's genes
Which of the following characteristics, structures, or processes is common to both bacteria and viruses?
 
genetic material composed of nucleic acid
Why are retroviruses considered a special class of viruses?
 
They transcribe RNA to DNA using reverse transcriptase.
What do we call a virus that attacks a bacterium?
 
phage
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
The operon model of the regulation of gene expression in bacteria was proposed by _____.
 
Jacob and Monod
Which of these is NOT a component of the lac operon?-lactose-utilization genes only -promoter only-regulatory gene only-operator only-promoter and operator
 
regulatory gene only
Regulatory proteins bind to _____.
 
the operator
In the presence of a regulatory protein the lac operon is _____.
 
not transcribed
Gel electrophoresis separates DNA fragments on the basis of what characteristic?
 
length
In gel electrophoresis DNA molecules migrate from _____ to _____ ends of the gel.
 
negative...positive
What is the most effective way to stop viral infections?
 
vaccines
What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?
 
transcription
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?
 
translation
What name is given to the process in which pre-mRNA is edited into mRNA?
 
RNA processing
Polypeptides are assembled from _____.
 
amino acids
RNA processing converts the RNA transcript into _____.
 
mRNA
Which one of the following is true of tRNAs?
 
Each tRNA binds a particular amino acid.
The anticodon of a particular tRNA molecule is
 
complementary to the corresponding mRNA codon
The direction of synthesis of an RNA transcript is _____.
 
5' —> 3'
Where does RNA polymerase begin transcribing a gene into mRNA?
 
It starts after a certain nucleotide sequence called a promoter.
What is the function of RNA polymerase?
 
It unwinds the double helix and adds nucleotides to a growing strand of RNA.
During RNA processing a(n) _____ is added to the 5' end of the RNA.
 
modified guanine nucleotide
During RNA processing a(n) _____ is added to the 3' end of the RNA.
 
a long string of adenine nucleotides
Spliceosomes are composed of _____.
 
snRNPs and other proteins
The RNA segments joined to one another by spliceosomes are _____.
 
exons
Translation occurs in the _____.
 
cytoplasm
How is translation initiated?
 
-The small ribosomal subunit binds to the mRNA-The tRNA bearing methionine binds to the start codon-The large ribosomal subunit binds to the small one-The start codon signals the start of translation
Which of the following mutations would be most likely to have a harmful effect on an organism?
 
a single nucleotide insertion downstream of, and close to, the start of the coding sequence
What is the process called that converts the genetic information stored in DNA to an RNA copy?
 
Transcription
DNA does not store the information to synthesize which of the following?
 
Organelles
Transcription begins at a promoter. What is a promoter?
 
A site in DNA that recruits the RNA Polymerase
Which of the following statements best describes the promoter of a protein-coding gene?
 
The promoter is a nontranscribed region of a gene.
What determines which base is to be added to an RNA strand during transcription?
 
Base pairing between the DNA template strand and the RNA nucleotides
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?
 
Complementary
What happens to RNA polymerase II after it has completed transcription of a gene?
 
It is free to bind to another promoter and begin transcription.
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.
 
three ... amino acid
The flow of information in a cell proceeds in what sequence?
 
from DNA to RNA to protein
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence?
 
introns ... exons
Which component is not directly involved in translation?
 
DNA
Which of the following mutations would likely be most dangerous to a cell?
 
Deletion of one nucleotide
What does a mutagen cause?
 
a change in the sequence of DNA
Which of the following characteristics, structures, or processes is common to both bacteria and viruses?
 
genetic material composed of nucleic acid
To cause a human pandemic, the H5N1 avian flu virus would have to
 
become capable of human-to-human transmission
A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have
 
T4 protein and T4 DNA
RNA viruses require their own supply of certain enzymes because
 
host cells lack enzymes that can replicate the viral genome
Viruses can vary with respect to all of the following characteristics except _____.
 
the presence or absence of metabolic machinery
A microbiologist analyzes chemicals obtained from an enveloped RNA virus that infects monkeys. He finds that the viral envelope contains a protein characteristic of monkey cells. Which of the following is the most likely explanation?
 
The viral envelope forms as the virus leaves the host cell.
Viruses that infect bacteria are called _____.
 
bacteriophages
HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is because _____.
 
the virus binds to specific receptors that are only present on certain immune cells
Cancer cells often have protein receptor molecules on their surfaces that differ from those on normal body cells. Given this fact, how might viruses be used to treat cancer?
 
Viruses could be engineered to infect only cancer cells by altering viral surface proteins to recognize only the receptors on cancer cells.
When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?
 
only the nucleic acid
The phage reproductive cycle that kills the bacterial host cell is a _____ cycle, and a phage that always reproduces this way is a _____ phage.
 
lytic ... virulent
In the lytic life cycle of phages _____.
 
the cell typically dies, releasing many copies of the virus
Restriction enzymes help defend bacteria against viral infections by _____.
 
cutting viral DNA once it has entered the cell
A phage that inserts itself into the host DNA is called _____.
 
lysogenic
A prophage is a(n) _____.
 
viral genome that has been incorporated into a bacterial cell's chromosome
What is the origin of the phospholipid membrane that envelops many animal viruses?
 
It is "stolen" from the host cell, but it contains some proteins encoded by the viral genome.
Why can flare-ups of herpesvirus infection recur throughout a person's life?
 
Herpesvirus can leave its DNA behind as minichromosomes in nerve cell nuclei. Stress can trigger another round of virus production, producing characteristic blisters and sores.
How do retroviruses, such as HIV, differ from other viruses?
 
They can transcribe a DNA copy from a RNA template.
Reverse transcription, carried out by retroviruses, is the process by which _____.
 
RNA information is copied into DNA
Which statement below is a correct comparison of a "regular" RNA virus and an RNA retrovirus?
 
Both produce protein coats via translation of mRNA.
When comparing DNA and RNA viruses, which mutate more quickly, and why?
 
RNA viruses, because no proofreading is done on RNA molecules
Vaccines for viral diseases are _____ and help prevent infection by _____.
 
harmless derivatives of pathogenic viruses ... stimulating the immune system to mount a defense against the actual pathogen
What is the function of hemagglutinin in the influenza virus?
 
Hemagglutinin is the protein that helps the influenza virus attach to host cells.
Birds act as a natural _____ for the influenza _____ virus.
 
reservoir ... A
Which of the following is an example of vertical transmission of a virus in plants?
 
An infected plant produces seeds that contain the virus, giving rise to infected progeny.
Plant viruses spread throughout the plant by way of _____.
 
plasmodesmata
Circular RNA molecules that function like a virus in plants are termed _____.
 
viroid
Prions are _____ that are thought to cause disease by _____.
 
abnormally shaped proteins ... inducing similar but normally shaped proteins in the brain to adopt the abnormal form
A new pathogenic form of influenza A can emerge when ________.
 
All of the listed factors likely contribute to the emergence of a new pathogenic strain of influenza A.
What is the prevailing hypothesis for the surprisingly low infection and mortality rate among people over 64 years of age during the 2009 H1N1 pandemic?
 
Older people were likely exposed to earlier H1N1 viruses that primed their immune systems for the virus of the 2009 pandemic.
The avian flu virus H5N1 is considered a greater long-term threat than the swine flu virus H1N1 because _____.
 
it has a significantly higher mortality rate
In eukaryotic cells, transcription cannot begin until

 
several transcription factors have bound to the promoter
Which of the following is not true of a codon?
 
It extends from one end of a tRNA molecule.
The anticodon of a particular tRNA molecule is
 
complementary to the corresponding mRNA codon.
Which of the following is not true of RNA processing?
 
Exons are cut out before mRNA leaves the nucleus.
Which component is not directly involved in translation
 
DNA

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