MCQs on Database Screening and Screening by Nucleic Acid Hybridisation – 1
1 - Question
The process of finding a particular member of the library which is having some defined properties is called as ___________
Explanation: The process of finding a particular member of the library which is having some defined properties is called as screening. Mostly screening is carried out for a particular coding sequence.
2 - Question
If for a particular organism sequence data is available and we have to simply search in the data through a computer, then this method is called as ___________
b) database search
c) in silico
d) electronic search
Explanation: The easiest way to find for a particular sequence is to exploit the genomic analyses. If the database is available for a particular sequence and the task is to simply search the data through the computer then the procedure is called in silico.
3 - Question
If we are having sequence data for a particular organism, but screening is carried out for homologues the program used is BLAST.
Explanation: Homologues are a group of organisms which contain similar sequences. Screening for such organisms can be carried out by using programs such as BLAST (Basic Local Alignment Search Tool). Search can be carried out within or for nucleotide and protein sequences.
4 - Question
If screening is carried out on the basis of sequences which are related to the desired sequence, then the process is called ___________
b) homologue search
d) partial search
Explanation: If the search is carried out on the basis of the related sequence rather than looking for the actual sequence then the process is termed as an annotation.
5 - Question
How many techniques are there for carrying out the screening of sequences encoding for RNAs?
Explanation: There are basically two techniques used for carrying out the screening of sequences encoding for RNAs. The first technique is based on nucleic acid hybridization and the second is based on coding function in vivo.
6 - Question
Choose the incorrect statement for colony or plaque lift.
a) It is the base for screening based on nucleic acid hybridization
b) It is also known as Grunstein-Hogness technique
c) It is based on the fact that which members of the library have the same sequence as the DNA probe
d) The library may be plaques on a bacterial lawn and in that case it is known as plaque lift
Explanation: Colony lift or plaque lift is the basis for nucleic acid hybridization. It is also known as Grunstein-Hogness technique named after the discoverer. It is based on the fact that which members of the library are complementary to the sequence of DNA probe can be known. The library may be plaques on a bacterial lawn and in that case it is known as plaque lift. There may be colonies on a plate and in that case, it is known as colony lift.
7 - Question
The screening of libraries us carried out by nucleic acid hybridisation and constitutes of following steps:
i) Peeling of membranes carrying away bacterial cells with it
ii) Cells are lysed and denaturing of DNA is being carried out
iii) Hybridization with labelled DNA
iv) Placing the membrane onto plate containing recombinant cells
Choose the correct sequence in which the steps are carried out (starting to ending). a) iv)-i)-ii)-iii)
Explanation: Firstly, the membrane is placed onto the plate containing recombinant cells. Then the membrane is peeled off and the bacterial cells are carried away with it. After this, cells are lysed and denaturing of DNA is done. It is followed by hybridization with labelled DNA and then visualization is done.
8 - Question
Choose the incorrect statement with respect to the membranes used for adhering of bacterial cells onto them.
a) Nitrocellulose membranes were preferred earlier
b) They bind DNA very efficiently
c) They can be handled easily without breakage
d) They are inflammable
Explanation: Nitrocellulose membranes were preferred earlier. They bind DNA very efficiently and are brittle thus can’t be handled efficiently without breaking. They are inflammable.
9 - Question
Nitrocellulose membranes are less sensitive than nylon membranes.
Explanation: Nylon membranes are less sensitive than nitrocellulose membranes. Though nylon membranes are used more often today but nitrocellulose membranes are more sensitive. To make nylon membranes more sensitive, they are derivatized.
10 - Question
What is used for lysing of bacterial cells and denaturation of DNA?
b) Sulphuric Acid
c) Sodium Hydroxide
Answer: c Explanation: The bacterial cells are lysed by the use of sodium hydroxide. The phage proteins and DNA are also denatured by the use of sodium hydroxide.