exam 4 bio
Check the answers that apply to catabolite repression and the lac operon.
-CAP is active when bound to cAMP -Adenyl cyclase synthesizes cAMP when glucose levels are low -The lac operon contains a CAP recognition site
Select the statements that are true of inducible operons to test your understanding of the differences between inducible and repressible operons.
-Inducible operons often contain genes for enzymes that function in catabolic processes. -The lac operon is an example of an inducible operon. -Inducible operons will be "turned on" in the presence of the substrate and "turned off" in its absence.
Conjugation
-involves a sex pilus -f factor -high frequency recombinants
Transduction
-lysogenic or lytic phage -can be specialized or general
Molecular chaperones function to _______.
-recognize unfolded or partially denatured proteins -prevent incorrect folding of proteins -fold newly formed proteins to their proper shape
A certain polypeptide is 100 amino acids in length. During translation of this polypeptide, how many amino acids entered through the A site of the ribosome?
99
New amino acids (other than the initial f-Met) enter at which site?
A
Translation is terminated when a stop codon is presented at the ________ site.
A
After the initiation step of protein synthesis, transfer RNAs carrying amino acids bind to the ribosome at the _______.
A site
translation is terminated when a stop codon is presented at the ________.
A site
Identify any item needed for the replication of the lagging strand of DNA.
DNA ligase Okazaki fragments primase
RNA primers are removed by the action of the enzyme ______.
DNA pol I
What enzyme synthesizes the daughter strands during DNA replication?
DNA polymerase
Exogenote
DNA that is transferred to recipient
What molecule initiates the formation of the replication bubble?
DnaA
During translation elongation, amino acids are brought to the ribosome with the help of ______.
EF-Tu
Which of the following occurs first in transcription?
Formation of a holoenzyme
Plasmids are small circular pieces of DNA
able to replicate independently of the chromosome.
in the absence of lactose, the lac repressor is
active and can bind to the operator.
After a tautomeric shift in adenine,
adenine bonds with cytosine.
Transcriptional control
attenuation regulatory protein binds dna riboswitch causes termination
Horizontal gene transfer is the transfer of DNA
between different genomes.
When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon.
cAMP; switches on
If E.coli is grown in a medium containing glucose and maltose in equal amounts, the gluose is broken down immediately followed by the maltose at a slower rate. This diauxic growth is an example of the use of
catabolite repression.
A mutation that causes a change in a single nucleotide in DNA
changes the corresponding nucleotide in mRNA, resulting in a different codon.
lysogenic
chill specialized transduction
Hfr strains contain the F factor integrated into their ________, rather than in the __________.
chromosome; cytoplasm
Horizontal gene transfer can occur via _________.
conjugation
Simple transposition is also termed ________ transposition.
conservative
A recombinant organism is one that
contains genes from another organism transferred via conjugation or some other method of horizontal gene transfer.
Posttranslational control
covalent modification of protein product feedback inhibition of end product
The main advantage of the ability of bacteria to carry out conjugation and other forms of recombination is that they Binary fission is essentially asexual, so these recombination mechanisms help bacteria vary their genetic makeup and respond better to changes in their environment.
create genetic diversity.
Vertical gene transfer is the transfer of DNA
during normal cell division.
Transformation with a linear DNA fragment may result in
either homologous recombination or unsuccessful transformation.
Following transformation, the mismatch repair system will repair
either the donor or the recipient strand.
A stop codon codes for an amino acid as well as the signal to stop. t or f
f
Excision repair takes place only in the presence of light. t or f
false
In transformation, both strands of donor DNA enter the recipient cell.t or f
false
The trp operon consists of ________ genes that encode tryptophan biosynthesis enzymes.
five
Endogenote
genome of recipient
A reciprocal exchange in which a pair of DNA with the same nucleotide sequence break and rejoin in a crossover is called __________ recombination.
homologous
In a tautomeric shift
hydrogen atoms move to form a base with altered hydrogen properties.
In the absence of tryptophan, the trp repressor is
inactive and cannot bind to the operator.
Translational control
inhibition by small ran molecules riboswitch blocks initiation binding of antisense rna
The ends of a simple transposable element contain
inverted repeats.
lytic
kill generalized transduction
The lac operon is expressed when glucose is
low and lactose is present
The Shine-Dalgarno sequence is found on the ________.
mRNA
DNA transformation involves the transfer of DNA via
naked DNA in solution.
transformation
naked DNA uptake by bacteria
When DNA is damaged by UV light and is not repaired
neither DNA replication nor transcription can occur and the organism will probably die.
The method used in horizontal gene transfer is
nonhomologous recombination.
Arrange the images in their proper order showing the potential fates of donor DNA once it enters a recipient cell.
on desktop
Label the experimental steps that must be performed to isolate a threonine auxotroph.
on desktop
When DNA from an ampicillin resistant organism is brought into an ampicillin sensitive organism by transformation and the product is grown on agar containing ampicillin
only the transformed cells will grow.
Translation is the synthesis of ______.
proteins from mRNA
Merozygote
recipient cell that is temporarily diploid as result of transfer process
The protein that promotes translation termination is called ________.
release factor
If you find that a particular plasmid has an R factor, the bacteria that has it will be R factors can make bacteria resistant to antibiotics such as penicillins, sulfonamides, or tetracycline.
resistant to antibiotics such as penicillins, sulfonamides, or tetracycline.
A mutation that changes a single nucleotide can result in a different amino acid being added into a protein. t or f
t
DNA mutations are passed on to a cell's progeny. t or f
t
In simple transposition, the transposable element ends up between two direct repeats of the target sequence. t or f
t
The enzyme transposase catalyzes simple transposition. t or f
t
the Rho protein is involved in the _____ stage of transcription.
termination
F plasmid
the F factor in its plasmid form
In light repair
the covalent bonds between the thymine dimers are broken.
prophage
the viral DNA that is embedded in the host cell's DNA
UV light damages DNA by causing covalent bonds to form between
thymine nucleotides next to each other on the same DNA strand.
At the E site _____.
transfer RNA is released
When a recipient cell acquires a piece of naked DNA from the environment, it is called
transformation.
If tryptophan is present in the cell's environment, tryptophan will bind to the _________.
trp repressor
Horizontal gene transfer occurs frequently between the nuclear, mitochondrial, and chloroplast genomes of some eukaryotes.t or f
true
In dark repair, the final phosphodiester bond is formed by DNA ligase. t or f
true
The inducer of the lac operon is an isomer of lactose.t or f
true
The trp repressor is a helix-turn-helix regulatory protein.t or f
true
When RNA polymerase is bound to the lac promoter sequence, transcription of the lac operon is on.t or f
true
Transformation
uptake naked dna fragments or plasmid -requires a competent recipient cell
phage
viruses that infect bacteria
What component binds to the initiation complex first?
IF3
Which of the following is true of the integration of a viral genome into the host chromosome?
Integration of the viral genome is a form of site-specific recombination.
What statement about peptidyl transferase is TRUE?
It catalyzes the formation of peptide bonds and is present in the 50S ribosomal subunits.
What statement is correct regarding sigma factor?
It recognizes the promoter region.
What statement is TRUE about tRNA?
No tRNA can recognize a stop codon.
After the ribosome moves to the next codon on the mRNA, the growing peptide chain is found in which position(s)?
P
The initiating transfer RNA, carrying formylmethionine, binds to which site?
P site
What type of bond is found connecting amino acids together during protein synthesis?
Peptide bonds
What cellular component is not involved in the initiation of translation?
RNA polymerase
When an F' plasmid acts as the donor in a mating, which of the following do(es) not happen?
Some chromosomal genes not on the plasmid are transferred.
Choose the statement below that is true about the characteristics of the F factor.
The F factor carries genes responsible for formation of sex pili, and has several IS elements to assist plasmid integration into host cell's chromosome.
In simple transposition,
a double-stranded piece of DNA is moved from one site to another.
Conjugation
a horizontal gene transfer between 2 living cells
Place each step in a logical order in this experiment designed to isolate revertants from a threonine auxotroph.
1. identify a threonine auxotroph 2.induce mutations with mutagen exposure 3. plate on master plate contains threonine to the left media lacks limiting factor: -produce replica plate without threonine incubate: -only REVERT strain will grow to the right media contains limiting factor: -produce replica plate (complete medium) incubate: -all strains grow
Arrange these replication proteins in the proper order in which they participate in DNA replication.1 = Primase2 = Helicase3 = Single-strand binding proteins4 = DNA polymerase I
2, 3, 1, 4
What combinations are correctly matched?
70S - ribosome
Donor DNA is combined with recipient DNA by homologous recombination.t or f
True
Transformation, transduction and conjugation are all mechanisms of horizontal gene transfer. In transformation, naked DNA enters a competent cell. During the process, double-stranded DNA binds to the cell and one strand is hydrolyzed . The single-stranded fragment that enters the cell is then integrated into the recipient's genome by homologous integration. During conjugation, a plasmid passes through a sex pilus into a recipient cell. When an F factor plasmid integrates into the host genome, it creates an Hfr cell. During conjugation with these cells, chromosomal DNA is transferred into the recipient cell, which becomes recombinant but is not considered an F+ cell since it did not receive the entire F factor plasmid. Transduction is the transfer of genetic material using a virus as a vector. Typically, during the assembly stage of the lytic cycle, the viral genome is packaged into the capsid . Occasionally, a random fragment of the host genome is packaged in error and is thus transferred to a neighboring cell as the virus continues its life cycle. This is known as generalized transduction. When prophageDNA is excised from the host genome, it may take with it a specific, adjacent DNA fragment, which is then transferred to the next viral-infected cell. This transfer of a known bacterial gene, is called specialized transduction.
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What occurs as the ribosome shifts down the mRNA by a distance of one codon
The tRNA that was in the A site moves into the P site.
What event occurs as the ribosome shifts down the mRNA by a distance of three nucleotides?
The tRNA that was in the P site moves into the E site.
What occurs as a result of translocation?
The tRNA that was in the P site moves into the E site.
What enzyme or protein prevents supercoiling of the DNA strands ahead of the replication bubble?
Topoisomerase
