Insertion Sequences, Transposon, And Integrons 2

Question 1

Creating mutants using transposons; often with suicide vectors

Answer 1

Transposon mutagenesis

Question 2

Properties of transposons for mutagenesis

Answer 2

Transpose at a fairly high frequency
Not be very selective in its target sequence
Should carry an easily selectible gene (ex. Antimicrobial resistance)
Have a broad host range for wide range of applicability

Question 3

Limitations of in vivo transposon mutagenesis

Answer 3

• Transposon should be introduced to suicide vector or else errors will be encountered if the vector replicates
• Possibility of multiple transposition
  events if it lacks target specificity
• Too many mutations encountered in the chromosome
• Plasmid or smaller DNA sequence is to be mutated

Question 4

Target DNA can either be _____ (or plasmids that replicate by themselves) or random linear pieces of the host chromosomal DNA that can be introduced by transformation

Answer 4

Replicons

Question 5

Tn5 and Himar1 originally from the horn fly ______; And has a _____ resistance gene

Answer 5

Haematobia irritans; Kanamycin

Question 6

Transposons with the transposase already attached are called

Answer 6

Transpososomes

Question 7

True or False: Transposon mutagenesis can be used for non-essential genes to avoid killing the host

Answer 7

True

Question 8

Only between specific sites of DNA

Answer 8

Site specific recombinases

Question 9

are site-specific recombinases which end up with the two sequences integrating with each other

Answer 9

Integrases

Question 10

Enumerate the steps for site specific recombinases

Answer 10

1.Excise the DNA in the two
recognition sites:
a. If in same DNA, resolvases and
invertases
b. Integrases if from different DNA
2. Join the cut ends while making sure the recognition sites meet each other.
3.Hold and orient the DNA to meet recognition sites.

Question 11

integrate the phage DNA to
host DNA

Answer 11

Phage integrase

Question 12

Example of Phage Integrase

Answer 12

Int enzyme of lambda phage

Question 13

Recognized sites for integration of lambda phage

Answer 13

• attB site of host DNA
• attP site of phage DNA

Question 14

Enzymes involved in lambda phage

Answer 14

Integrase (Int)
Excisase (Xis)

Question 15

similar regions in transposons that contain antibiotic resistance genes

Answer 15

Integrons

Question 16

Integrons that are found in chromosome

Answer 16

Superintegrons

Question 17

Parts of Integrons

Answer 17

• Integrase gene (intl1) that
  facilitates recombination
• Attachment site (attI)
  recognized by integrons for
  recombination and often next
  to intl1
• Promoter (pc) for transcription
  of the genes within the integron
  and next to attI

Question 18

are short DNA segments inserted into integrons or small circular DNA

Answer 18

Cassettes

Question 19

Large segments of DNA often composed of several genes related to pathogenicity

Answer 19

Genetic pathogenicity islands (PAIs)

Question 20

Genes responsible for toxic shock syndrome in Staphylococcus aureus

Answer 20

PAI SaPI1

Question 21

True or False: PAIs cannot be transferred via phages such as phage 80a

Answer 21

False

Question 22

Resolves cointegrates of
transposition by recognizing the
res sequence

Answer 22

Resolvases

Question 23

True or False: Resolvases are applicable to plasmids in dimer formation

Answer 23

True

Question 24

promote site-specific recombination but the two DNA sites are in reverse orientation in relation to each other (invertible sequences); Useful for evading immune responses and is reversible

Answer 24

DNA invertases

Question 25

Salmonella H1 to H2 flagellin often invert using the ______ through recombination between the sites hixL and hixR.

Answer 25

Hin invertase

Question 26

Either a tyrosine (Y) or serine (S) is in the active center of the
recombinases

Answer 26

Y and S recombinases

Question 27

____ recombinase that recognizes loxP site for Y recombinase

Answer 27

Cre

Question 28

Y and S recombinases form what junction? 3’-ends join the 5’-ends

Answer 28

Holliday junction