You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium. You have isolated a mutation that causes constitutive melibiase activity, which you designate MelA–. P1 phage mapping experiments using a Tn5 insertion linked to Mel1 show that MelA– is not linked to Mel1. Moreover you find that when an amber suppressor is introduced into a MelA– mutant, normal melibiase regulation is restored. Classify the MelA– mutation on the basis of genetic properties,  make a proposal for the type of regulatory functions affected by the MelA– mutation?

TLS Online TPP Program

#Question id: 13078

#Unit 13. Methods in Biology

RFLPs have several unique advantages except this one;

TLS Online TPP Program

#Question id: 13079

#Unit 13. Methods in Biology

Name of that sophisticated equipment which used to the oligonucleotide, that serve as a primer in RAPDs is usually obtained by in vitro DNA synthesis,

TLS Online TPP Program

#Question id: 13080

#Unit 13. Methods in Biology

In RAPDs amplification will take place only of those regions of the genome that have the 

TLS Online TPP Program

#Question id: 13081

#Unit 13. Methods in Biology

Correct statements about RAPD’s

A. RAPD polymorphism is detected by using oligonucleotides usually more than 10 bases long of random sequences as primers in a reaction.

B. In a strain which has in genomic DNA sequences complementary to the primer oligonucleotide, PCR products will be detected in the gel,

C. Typical RAPD markers show limited variation between parents, especially in naturally inbreeding species.

D. RAPDs are more sensitive than RFLPs to experimental conditions making them more difficult to be consistent and reproducible.

TLS Online TPP Program

#Question id: 13082

#Unit 13. Methods in Biology

Statement: AFLP shares some features of both RFLP and RAPD analyses.

Explanations: I. It uses restriction enzyme-digested genomic DNA as template for PCR amplification using primers that contain the restriction enzyme recognition sites plus a number of, usually 2-3, arbitrary nucleotides.

II. AFLPs are faster, less labour intensive and provide more information than RFLPs, and they are highly reproducible, which is a great advantage over RAPDs.

TLS Online TPP Program

#Question id: 13083

#Unit 13. Methods in Biology

The genomic DNA of an organism is digested with two restriction enzymes; one of the, PstI (CTGCA/G), while the other., MseI (T/TAA). This would generate the following 3 types of DNA fragments: 

(1) both ends cleaved by PstI (Pst-Pst), 

(2) both ends cleaved by MseI (Mse-Mse), and 

(3) one end generated by each of the two enzymes (Pst-Mse). 

the most frequent fragments in decreasing order,