Exam 4: possible Flashcards
Which of the following is false?
a. Transposition is a process of nonhomologous recombination that requires a transposase.
b. Transposons were first found in bacteria in 1950’s and later in corn.
c. Homologous recombination requires that the two DNAs base-pair, meaning that they must have the same sequence.
d. Nonhomologous recombination does not depend on extensive homology between the two DNAs.
IRs are:
a. Cis-acting elements
b. Found at the ends of a transposablef
element.
c. Stand for inverted repeats
ANS:
d. All of the above.
Which of the following statements is/are true about the N protein in l?
a. N protein is an antiterminator that binds to the nutL and nutR sequences on the DNA.
b. N binds to nutR (and nutL) motif on the transcript, changing its conformation to help with the recruitment the RNA polymerase.
c.The expression of N causes transcription to continue past the terminators t1Land t1R. d. a and c are true
e. b and c are true
ANS: B AND C ARE TUE
Which of the following statements is false about Tn10?
Forms a cointegrate as an intermediate
If lambda phage were unable to express the Cro repressor protein, what would happen?
It would never enter the lytic pathway.
Which of the following statements is/are false about Tn3?
Transpose by a cut-and-paste mechanism
In the lab this semester you used the antibiotic anhydrotetracycline (ATc). Why did you use it?
To induce expression of Rv2275 and cyp121
Which of the following statements is true?
. Half of human chromosomal DNA is made of transposons.
A concatemer is a:
combination of two or more repeated nucleotide sequences covalently linked together.
A 5-kbp plasmid with cos sites can be packaged in l capsid?
False
A nonsense mutation in tpnR gene of Tn3 results in all, except?
Inhibition of transposition.
Which of the following of statements is false about the role of CII in the formation of lysogens after l infection?
CII is an inhibitor of FtsH (HflB) protease that degrades CIII.
Q of phage lambda is an antitermination protein that loads on RNA polymerase at qut site on the mRNA and prevents termination at downstream terminators, including tR’.
TRUE/False
FALSE
A virus that integrates its genome in the its host’s chromosome is said to be:
lysogenic
_______ and ________ both contain inverted repeats and encode transposase.
insertion sequences / transposons
Which of the following statements is/are true about transposition of composite transposons?
ALL of the above are ture
If a mutation were to occur in lambda phage that made it unable to express integrase, what would happen?
It would be unable to recombine with the bacteria chromsome.
Which type of regulator(s) specifically bind to operator regions of DNA?
Repressors
Which of the following happens to initiate specialized phage transduction?
Prophage integrates into the host genome AND bacteriophage enters lysogeny.
Transposons inactivate genes by:
Inserting randomly in chromosomal
DNA.
Which of the following statements is/are true?
IS are reversible at high frequency.
You need to prepare 10 ml of growth media supplemented with 100 ng/ml of anhydrotetracycline (ATc), The stock solution of ATc is at 1 mg/ml. what is the volume of ATc to be added?
1 uL
Lysogeny probably carries a strong selective advantage for the host cell because it:
confers resistance to infection by viruses of the same type.
Why are some transposons important?
ALL OF THE ABOVE
Why is it recommended to incubate the commercial lambda DNA digested with Hind III before using it for DNA electrophoresis analysis on agarose gel?
It prevents the two fragments with cos sites to anneal to each
other.
Which of the following statements is/are true?
The transposon inserts into a target DNA using staggered joins to the top and bottom strands.
b. The insertion process leaves gaps flanking the transposon that must be filled by DNA ligase, leading to the formation of inverted repeats.
c. Length of direct repeats can varied from 2 to 9 bp.
A AND B ARE TRUE
Both insertion mutations and knock-out mutations by homologous recombination can cause loss of function; however, with knock-out mutations,
the experiment chooses the gene that is inactivated
