In gel electrophoresis, separated DNA fragments can be visualized with the help of [2020]
acetocarmine in bright blue light
ethidium bromide in UV radiation
acetocarmine in UV radiation
ethidium bromide in infrared radiation
(2)
In gel electrophoresis, separated DNA fragments can be visualised only after staining the DNA with a compound i.e., ethidium bromide and followed by exposure to UV radiation as bright orange coloured bands.
Following statements describe the characteristics of the enzyme restriction endonuclease. Identify the incorrect statement. [2019]
The enzyme recognises a specific palindromic nucleotide sequence in the DNA.
The enzyme cuts DNA molecule at identified position within the DNA.
The enzyme binds DNA at specific sites and cuts only one of the two strands.
The enzyme cuts the sugar-phosphate backbone at specific sites on each strand.
(3)
The restriction endonuclease enzyme inspects the length of a DNA sequence. Once it recognises specific sequence, it binds to the DNA and cuts each of the two strands of the double helix at specific points in their sugar phosphate backbone. Special sequence in the DNA recognised by restriction endonuclease is called palindromic nucleotide sequence.
A selectable marker is used to [2019]
help in eliminating the non-transformants, so that the transformants can be regenerated
identify the gene for a desired trait in an alien organism
select a suitable vector for transformation in a specific crop
mark a gene on a chromosome for isolation using restriction enzyme.
Given below are four statements pertaining to separation of DNA fragments using gel electrophoresis. Identify the incorrect statements.
(i) DNA is negatively charged molecule and so it is loaded on gel towards the anode terminal.
(ii) DNA fragments travel along the surface of the gel whose concentration does not affect movement of DNA.
(iii) Smaller the size of DNA fragment larger is the distance it travels through it.
(iv) Pure DNA can be visualized directly by exposing UV radiation.
Choose correct answer from the options given below: [2019]
(i), (iii) and (iv)
(i), (ii) and (iii)
(ii), (iii) and (iv)
(i), (ii) and (iv)
DNA is a negatively charged molecule, so they can be separated by forcing them to move towards the anode under an electric field. DNA fragments separate according to size through the pores of agarose gel. The separated DNA fragments can be visualised only after staining the DNA with a compound known as ethidium bromide then followed by exposure to UV radiation.
Which of the following is commonly used as a vector for introducing a DNA fragment in human lymphocytes? [2018]
Retrovirus
Ti plasmid
phage
pBR322
Retroviruses cause cancer in animals including humans. So modified retroviruses are used to transfer desirable genes into animal cells. It is used in gene therapy, in which lymphocytes from blood of patient are taken and grown in culture medium outside the body, a functional gene is introduced by using a retroviral vector into these lymphocytes which are again reintroduced into the patient body.
The DNA fragments separated on an agarose gel can be visualised after staining with [2017]
acetocarmine
aniline blue
ethidium bromide
bromophenol blue
The separated DNA fragments can be seen only after staining them with a compound known as ethidium bromide (EtBr) followed by exposure to UV radiation as bright orange coloured bands.
DNA fragments are [2017]
negatively charged
neutral
either positively or negatively charged depending on their size
positively charged
A gene whose expression helps to identify transformed cell is known as [2017]
vector
plasmid
structural gene
selectable marker
Some genes called "selectable markers" help in selecting those host cells which contain the vectors (transformants) and eliminating the non-transformants.
What is the criterion for DNA fragments movement on agarose gel during gel electrophoresis? [2017]
The smaller the fragment size, the farther it moves.
Positively charged fragments move to farther end.
Negatively charged fragments do not move.
The larger the fragment size, the farther it moves
Electrophoresis is a technique used for the separation of substances of different ionic properties. Since the DNA fragments are negatively charged molecules, they can be separated by allowing them to move towards the anode. DNA fragments move towards the anode according to their molecule size through the pores of agarose gel. Thus, the smaller fragments move farther away as compared to larger fragments.
A foreign DNA and plasmid cut by the same restriction endonuclease can be joined to form a recombinant plasmid using [2016]
EcoRI
Taq polymerase
polymerase III
ligase
Ligase is a class of enzymes that catalyse the formation of covalent bonds using the energy released by the cleavage of ATP. Ligases are important in the synthesis and repair of many biological molecules, including DNA ligase and used in genetic engineering to insert foreign DNA into cloning vectors.
