Biotechnology Principles and Processes Test - 18

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 are commonly classified into three types, which differ in their structure and whether they cut their DNA substrate at their recognition site, or if the recognition and cleavage sites are separate from one another. To cut DNA, all restriction enzymes make two incisions, once through each sugar-phosphate backbone i.e., each strand of the DNA double helix. Restriction endonuclease was discovered by Smith and North. 

• Recombinant DNA technology enables individual fragments of DNA from any genome to be inserted into vector DNA molecules, such as plasmids. 
• The plasmids are used to transfer this rDNA into the host cell where multiple copies of the DNA fragments can be amplified (multiplied).
• Each amplified fragment is called a DNA clone and the process of producing multiple copies of desired DNA sequence through rDNA technology is gene cloning.
  

Thus, the correct answer is option C. 

Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain. Some, such as deoxyribonuclease I, cut DNA relatively non-specifically, while many, typically called restriction endonucleases or restriction enzymes, cleave only at very specific nucleotide sequences.

Gel Electrophoresis is a technique commonly used in laboratory to separate charged molecules like DNA, RNA, Proteins according to their size. Charged molecules move through a gel when an electric current is passed across it. An electric current is applied across the gel so that one end of the gel has a positive charge and the other end has a negative charge. The movement of charged molecules is called migration. Molecules migrate towards the opposite charge. A molecule with a negative charge will therefore be pulled towards the positive end (opposites attract). The gel consists a permeable matrix, a bit like a sieve, through which molecules can travel when an electric current is passed across it. Smaller molecules migrate through the gel more quickly and therefore travel further than larger fragments that migrate more slowly and therefore will travel a shorter distance. As a result the molecules are separated by size.
So, the correct option is option C.

Correct Option:A
Explanation:

Penicillin made a difference during the first half of the 20th century. Penicillin helped reduce the number of deaths and amputations of troops during World War II. It helped cure patients from Streptococcal septicemia or blood poisoning. According to records, there were only 400 million units of penicillin available during the first five months of 1943.

Correct Option: E

Restriction endonucleases are called as molecular scissors. It is because of the special feature of these enzymes to cut it at desired sites of DNA in the technique of genetic engineering.