The sequence of σ54 is distinctly different from that of all the σ70-like factors, some characteristics about σ54 is given below;

a) The σ54-RNA polymerase binds to the glnA promoter and immediately melt the DNA strands and initiate transcription

b) σ54-polymerase does not require ATP hydrolysis to separate the strands at a start site only require activator such as   NtrC

c) σ54-RNA polymerase initiate transcription of glnA promoter only when it is activated by NtrC

d) ATP hydrolysis is required for activation of bound σ54-RNA polymerase by phosphorylated NtrC

Which of the following from the bove combination is INCORRECT?

TLS Online TPP Program

#Question id: 18956

#Unit 13. Methods in Biology

It is possible to calculate the number of clones that must be present in a gene library to give a probability of obtaining a particular DNA sequence. This formula is:

 

where N is the number of recombinants, P is the probability and f is the fraction of the genome in one insert. Thus for the E. coli DNA chromosome of 5 × 10 ⁶ bp andan insert size of 20 kb ( f = 0.004), the number of clones needed ( N ) would be 1 × 10 ³ ,with a probability of P will be

TLS Online TPP Program

#Question id: 18957

#Unit 13. Methods in Biology

A DNA fragment of 5000bp needs to be isolated from E.coli (genome size 4x103kb) genomic library. The minimum number of independent recombinant clones required to represent this fragment in genomic library are

TLS Online TPP Program

#Question id: 18958

#Unit 13. Methods in Biology

The number of clones to represent this fragment in genomic library with a probability of 95% are

TLS Online TPP Program

#Question id: 18959

#Unit 13. Methods in Biology

 Vectors used for construction of genomic libraries, and their capacity is given match them correctly

A- λ EMBL series                                                                                   I - 300kb - 1,400 kb

B - Cosmids                                                                                                 II - 45 kb

C – BACs and YACs (high capacity vectors)                                             III - 20kb

TLS Online TPP Program

#Question id: 18960

#Unit 13. Methods in Biology

cDNA library do not require very large vectors hence which of the following is commonly used in cDNA library

TLS Online TPP Program

#Question id: 18961

#Unit 13. Methods in Biology

When a cDNA library is generated by first removing those mRNA or cDNA sequences that are common to two sources, e.g., two different Cell types, such a library is called