Biotechnology Principles and Processes Test - 71

Correct option: B

• A restriction enzyme is an enzyme that cleaves the DNA molecule at a specific site called a restriction site. It is used to cut DNA into smaller fragments. 
• Different restriction enzymes have different restrictions sites and hence cut different yet specific DNA sequences. There are two types of restriction enzymes - endonucleases and exonucleases. 
• Exonucleases cut DNA from the end while the endonucleases cut the DNA by recognizing a specific sequence of base pairs. Alu I is an exonucleases restriction enzyme that recognizes and cuts at the AG^CT site. 

Isolation of the Genetic Material (DNA):

Nucleic acid is the genetic material, which is present in all living organisms. In majority of organisms, this is present in the form of deoxy-ribonucleic acid (DNA). DNA must be present into pure form, i.e., free from other macro-molecules (like proteins, RNA, enzymes, etc.) in order to cut the DNA with restrictor enzymes.

Isolation of genetic material (DNA) is carried out in the following steps:

(a) Since the DNA is enclosed within the membranes, so, in order to release DNA along with other macro-molecules such as proteins, polysaccharides and lipids, bacterial cells/plant or animal tissues are treated with the enzyme lysozyme (bacteria), cellulose (plant cells), chitinase (fungus), respectively.

(b) RNA can be removed by the treatment with ribonuclease, whereas proteins can be removed by the treatment with protease.

(c) Other molecules can be removed by appropriate treatments and ultimately purified DNA will precipitate out, after the addition of chilled ethanol. This can be seen as collection of fine threads in the suspension.

So, the correct answer is “Precipitation of DNA”.

A restriction enzyme (or restriction endonuclease) is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Restriction enzymes recognize a specific sequence of nucleotides and produce a double-stranded cut in the DNA. Many of them are palindromic, meaning the base sequence reads the same backwards and forwards. Recognition sequences in DNA differ for each restriction enzyme, producing differences in the length, sequence and strand orientation (5' end or the 3' end) of a sticky-end of an enzyme restriction. If we cut the DNA with EcoR1, the DNA would be cut right in the middle. All the pieces would be the same size, which would be 15 kb long. Hence 5' GAATTC 3' ; 3' CTTAAG 5' palindrome sequence can be easily cut at about the middle by EcoR1 enzyme.
So, the correct option is option A.

In the PCR, the process of replication of DNA is repeated many times, the segment of DNA can be replicated to approximately 1 billion copies and this is achieved by the use of thermostable DNA polymerase which is isolated mainly from thermostable bacteria like Thermus aquaticus. The availability of this thermostable DNA polymerase popularised the PCR. So the correct option is D.

Reporter genes are those genes that are attached to the genes of the other organisms to obtain their process and details. These genes are often used to obtain gene of interest or desirable gene, sometimes they are also used as a selectable marker. They are placed at the upstream position of the gene of interest to contain their gene expression and functions. Some of the examples are lac Z, GFP (Green fluorescent protein) etc. Lac Z is the reporter genes and acts upon the beta-galactosidase gene.

Polymerase chain reaction is a process in which multiple copies of DNA of interest is synthesised invitro. The process involves three steps Denaturation , Annealing , Extension.So the correct option is option A.