Exam 4: possible

Question 1

Which of the following is false?

Answer 1

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.

Question 2

IRs are:

Answer 2

a. Cis-acting elements
b. Found at the ends of a transposablef
element.
c. Stand for inverted repeats
ANS:
d. All of the above.

Question 3

Which of the following statements is/are true about the N protein in l?

Answer 3

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

Question 4

Which of the following statements is false about Tn10?

Answer 4

Forms a cointegrate as an intermediate

Question 5

If lambda phage were unable to express the Cro repressor protein, what would happen?

Answer 5

It would never enter the lytic pathway.

Question 6

Which of the following statements is/are false about Tn3?

Answer 6

Transpose by a cut-and-paste mechanism

Question 7

In the lab this semester you used the antibiotic anhydrotetracycline (ATc). Why did you use it?

Answer 7

To induce expression of Rv2275 and cyp121

Question 8

Which of the following statements is true?

Answer 8

. Half of human chromosomal DNA is made of transposons.

Question 9

A concatemer is a:

Answer 9

combination of two or more repeated nucleotide sequences covalently linked together.

Question 10

A 5-kbp plasmid with cos sites can be packaged in l capsid?

Answer 10

False

Question 11

A nonsense mutation in tpnR gene of Tn3 results in all, except?

Answer 11

Inhibition of transposition.

Question 12

Which of the following of statements is false about the role of CII in the formation of lysogens after l infection?

Answer 12

CII is an inhibitor of FtsH (HflB) protease that degrades CIII.

Question 13

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

Answer 13

FALSE

Question 14

A virus that integrates its genome in the its host’s chromosome is said to be:

Answer 14

lysogenic

Question 15

_______ and ________ both contain inverted repeats and encode transposase.

Answer 15

insertion sequences / transposons

Question 16

Which of the following statements is/are true about transposition of composite transposons?

Answer 16

ALL of the above are ture

Question 17

If a mutation were to occur in lambda phage that made it unable to express integrase, what would happen?

Answer 17

It would be unable to recombine with the bacteria chromsome.

Question 18

Which type of regulator(s) specifically bind to operator regions of DNA?

Answer 18

Repressors

Question 19

Which of the following happens to initiate specialized phage transduction?

Answer 19

Prophage integrates into the host genome AND bacteriophage enters lysogeny.

Question 20

Transposons inactivate genes by:

Answer 20

Inserting randomly in chromosomal

DNA.

Question 21

Which of the following statements is/are true?

Answer 21

IS are reversible at high frequency.

Question 22

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?

Answer 22

1 uL

Question 23

Lysogeny probably carries a strong selective advantage for the host cell because it:

Answer 23

confers resistance to infection by viruses of the same type.

Question 24

Why are some transposons important?

Answer 24

ALL OF THE ABOVE

Question 25

Why is it recommended to incubate the commercial lambda DNA digested with Hind III before using it for DNA electrophoresis analysis on agarose gel?

Answer 25

It prevents the two fragments with cos sites to anneal to each
other.

Question 26

Which of the following statements is/are true?

Answer 26

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

Question 27

Both insertion mutations and knock-out mutations by homologous recombination can cause loss of function; however, with knock-out mutations,

Answer 27

the experiment chooses the gene that is inactivated