Chapter 11: Biotechnology: Principles and Processes

Ans: Gene cloning is a process by which multiple copies of a specific gene can be produced. This is done by: 

Selecting specific gene

The selected gene is ligated to a vector.

Recombinant DNA or rDNA is produced.

This rDNA is now transformed into a bacterial cell.

As bacteria reproduce, their colony increases and each progeny will have that rDNA.

Thus, the number of copies of genes increases.

Ans: Biotechnology is a branch of science in which living organisms are used to produce products for humankind. So, yes, both winemakers and molecular biologists are biotechnologists.

Ans: When a DNA molecule is created by ligating a gene to a plasmid vector then it becomes a circular DNA, if by mistake exonuclease is added to the tube it will not affect the process because now DNA is not having a free end and thus exonuclease will not get a substrate to show its action.

Ans: Restriction enzymes that are used in the construction of recombinant DNA are endonucleases which cut the DNA at ‘specific-recognition sequence’ because specific-recognition sequence in the DNA provide sticky ends at which recombination of genes takes place which further leads to replication of selected gene and if endonucleases fail to cut the DNA at specific-recognition sequence the recombination will fail to occur.

Ans: A plasmid DNA and linear DNA have one site for a restriction endonuclease, when cut and separated on agarose gel then circular DNA opens up to resemble a single linear DNA and linear DNA divides into two fragments after cleavage. Thus, circular DNA shows one band and linear DNA shows two bands.

Ans: While doing gel electrophoresis then the gel is added with a compound called Ethidium Bromide which stains the DNA so when DNA fragments are separated then it is put under UV radiation, fluorescence gives orange light. Thus, DNA fragments appear as orange bands in the presence of Ethidium Bromide and UV light.

Ans: The function of the selectable marker is to identify and eliminate non-transformant DNA and selectively allow the growth of transformants. So, in the absence of a selectable marker, it is not possible to segregate transformants and non-transformants.

Ans: A mixture of fragmented DNA was electrophoresed in an agarose gel. After staining the gel with ethidium bromide, no DNA bands were observed the following possible reasons can be behind this:

• Maybe DNA gets contaminated because of the accidental addition of nuclease enzymes.

• Maybe electrodes are put on the wrong side i.e., anode towards the loading well. As DNA is negatively charged, it moves back towards the anode.

• Maybe the quantity of ethidium bromide was not sufficient.

Ans: CaCl2 provides the divalent ion i.e., Ca²⁺ which creates transient pores on the bacterial cell wall which then facilitates the entry of foreign DNA in the bacterial cell. So, because of divalent ions, the cell becomes competent and it increases the efficiency of uptake of DNA through the pores.

Ans: If antibiotics are not added in the growing medium then the bacteria do not have any pressure to create antibiotic-resistant genes as they are easily surviving and as a result, desirable genes would not produce.