What is is called when the H-bonds between two DNA strands break?
Denaturation or melting
Because of ...............one strand of DNA can always be used as the template for the synthesis of another.
What three types of RNA is DNA transcribed to?
mRNA, tRNA, rRNA
This type of RNA is simply amessenger and it is always translated to give a protein product
This RNA plays a very important role in thetranslational function of the ribosome
This RNA binds to amino acids anddelivers them to the ribosome where the polypeptide chain (that will fold intoa protein) is being translated from the mRNA code
Only mRNA, but not rRNA or tRNA
D. is translated to form protein product.
Replication of a circular chromosome or a plasmid always begins ata point on the plasmid called the............and can proceed in..............
origin of replication, both directions
Replication of the E. coli chromosomea. initiates when an RNA polymerase enzyme called Tusunwinds a short stretch of DNA.
b. originates and terminates at the same location.
c. results in the transient formation of a region of newlysynthesized DNA called the replication bubble.
b. originates and terminates at the same location
Before replication begins...........unwind the helix and..............relieve the tension.
At the replication fork, a single complex called the............(containing DNA polymerases) synthesizes both the leading and lagging strands.
DNA polymerase can only synthsize DNA in the..............direction.
5' to 3'
This enzyme is used to form small RNA primers in the first step of the synthesis of the lagging strand.
DNA polymerase requires a............in order to beigin synthesizing DNA.
Which of the following is/are true about DNAreplication?a. It starts at the origin of replication.
b. It is bidirectional
c. It requires an RNA primer to get started.
d. It is semiconservative.
e. All of the above.
e. All of the above
What is the sequence of the RNA transcript for the portion ofthe gene shown here?
RNA always looks like the..............strand of DNA except...........is replaced by............
coding, T, U
The..........is the transcription initiation site.
In prokaryotes,there is often more than 1 gene under control of the same promoter.This is called an
Promoters are consensus sequences of nucleotides that lie..............of the gene
The...................is the subunit of...............that recognizesthe promoter
sigma factor, RNA polmerase
Which of the following is/are involved with theinitiation phase of transcription but not with elongation ortermination?
E. both b and c
RNA polymerase is used in elongation and the hairpin loop is used in termination.
(T or F) RNA polymerase requires a primer in order tobegin transcription
(T or F) A DNA template strand can betranscribed by more than one RNA polymerase enzymes ata time.
Which terminal of the mRNA transcript is readily available while transcription is still taking place (the 5' or the 3')?
What are the two types of termination?
Termination due to hairpin loop formation and Rho-dependent termination
Which statement/s regarding prokaryotic translationis/are TRUE?
E. a and c
Where does translation occur?
tRNA's can recognize more than one codon. This is called..........
What is the Shine-Dalgarno sequence?
Ribosome binding site
The ribosome binding site is typically............................from the start codon.
7 nucleotides upstream
Which one of the following correctly summarizesthe order of events that take place during the elongationphase of translation?
1. The initiating tRNA carrying the f-Met residue is boundin the P-site.
2. The ribosome advances the distance of one codon alongthe mRNA and the initiating tRNA + f-Met leave throughthe E-site.
3. The f-Met residue is covalently bound to the amino acidcarried by the tRNA in the A-site.
4. A tRNA carrying the amino acid that corresponds to thesecond codon binds to the A-site.
D. 1, 3, 4, 2
In which direction is the polypeptide chainsynthesized?
a. from the carboxyl terminal to the aminoterminal.
b. from the amino terminal to the carboxylterminal.
a. from the carboxyl terminal to the aminoterminal
Which of the following is / are involved in replication?
D. DNA polymerase
Which statement about eukaryotic and prokaryoticgene expression is FALSE?
A gene that is always expressed is...............
What is an operon?
A promoter, in prokaryotes, that controls more than 1 gene.
A................blocks transcription by binding to an operator.
A(n)..............facilitates transcription by binding to an activator binding site.
What is a corepressor?
A molecule that a repressor sometimes requires must be bound to it before it can bind to the operator site.
What is an inducer? Give an example.
A molecule that binds to the repressor to keep it from binding to the operator site. Example: lac operon
What are two mechanisms by which the genotype of an organism can change?
mutation and selection
What is a neutral mutation?
A mutation that codes for a simliar enough amino acid that the overall outcome is not affected.
What is a base substitution?
Incorporation of an incorrect base
What does the addition or removal of a nucleotide lead to?
Frameshift mutations, often are null or knockout mutations
What are transposons?
They disrupt the gene into which they insert
What do alklylating agents do?
Add methyl groups to bases causing mispairings. Example: nitrogen mustard
What are base analogs?
They resemble a base so closly that they are incoporated into DNA insted of the normal base. Example: 5-bromouracil
What are intercalating agents?
They insert between adjacent base pairs. Often leads to the addition of an extra nucleotide and frameshift mutation. Example: Ethidium bromide
What three ways can mutants be detected?
1) observation if they cause a visible change in phenotype
2)By direct selection if the mutant will grow in the prescence of some substance that the wild type cells will not grow in (ex: streptomycin resistant mutants)
3)By indirect selection if the mutant is an auxotrophic mutant and needs something for growth that the prototrophic cells do not need.
An organism that is Trp
B. is a prototroph
What does the Ames test do?
Identifies potentila carcinogens by testing chemicals for their ability to cause mutation in a bacerial system. Particular system used is His-auxotroph of Salmonella
A student doing his summer internship at RockyMountain Labs, performs the Ames Test on a chemicalthought to be a potential carcinogen. After incubating theGSA plate, the student notes that there are many morecolonies on the plate than are seen on a negative controlplate. Which conclusion/s does the student make?
What are the three mechanisms of lateral gene transfer?
transformation, transducation, conjugation
What is a recombinant cell?
When an exogenote becomes a stable part of the recipien's genome.
Transformation, transduction and conjugation
Which statement/s describe/s DNA-mediatedtransformation?
Which statement/s about DNA-mediatedtransformation is/are FALSE?
If plasmid DNA is taken up by the cell during transformation, then the plasmid remains in the...............and replicates....................
What is entry?
A double-stranded piece of DNA adheres to the cellsurface. One strand is degraded by nucleases and the other strandenters the cell. This mechanism varies amongst different genera.
What is integration?
ThessDNA aligns with a region on the recipient cell’s chromosome towhich it is highly homologous. (**HIGHLY HOMOLOGOUS =VERY SIMILAR). The recipient DNA separates and pairs with thedonor DNA. A nuclease cleaves the recipient cell’s DNA andreleases the homologous section into the cytoplasm to be degradedby nucleases. This is called BREAKAGE. The donor DNA nowreplaces the recipient DNA = REUNION. This forms a region ofheteroduplex DNA (one strand is donor DNA, the other isrecipient DNA).
After donor DNA has integratedinto the recipient cell’s chromosome, is stable transformation alwaysaccomplished? Why?
not always, sometimes the mismatchrepair system catches errors and the sequence is unchanged. There’sa 50/50 chance in terms of which strand will be repaired.
During..................a bacteriophage (termed adefective phage) accidentally packages bacterial DNA into its capsidhead rather than phage DNA.
Which statement about generalized transduction isFALSE?
What is conjugaion?
The transfer of DNA from a donor to a recipient cellvia cell-to-cell contact.
Which one of the following is the most important means of plasmid transfer?
Cells that are F+ contain the............plamid.
The F- plasmid encodes for what? What is its purpose?
The F pilus which serves as a bridge over which the F plasmid can be transferred from the donor cell to the F-(recipient cell). Always unidirectional and only the plasmid is transferred.
What are the steps of conjugation?
The F (fertility) plasmid
In lab, we worked with a strain of Staphylococcus aureus that was resistant to penicillin. Which one of thefollowing would probably be seen in this strain of S. aureus?