CBSE Questions for Class 12 Medical Biology Biotechnology: Principles And Processes Quiz 1 - MCQExams.com

• In 1997, the first transgenic cow, Rosie, produced human alpha-lactalbumin enriched milk at 2.4 grams per litre.
• This transgenic milk is a more nutritionally balanced product than natural bovine milk and could be given to babies or the elderly with special nutritional or digestive needs. 
• Restriction enzymes are DNA-cutting enzymes found in bacteria (and harvested from them for use). Because they cut within the molecule, they are often called restriction endonucleases.
• They are not used for isolation of DNA.
• Downstream processing refers to the recovery and purification of biosynthetic products, particularly pharmaceuticals, from natural sources such as animal or plant tissue or fermentation broth, including the recycling of salvageable components and the proper treatment and disposal of waste.
• Downstream processing is usually considered a specialized field in biochemical engineering. 
• Pathogens like the bacteriophage vectors are disarmed and allowed to infect the bacterial cells. They transfer the rDNA into the host.
  Hence, the correct option is D.
  

• DNA or genomic source is digested with a restriction enzyme and separated by electrophoresis. The DNA is denatured into single strands by incubation with NaOH.
• The DNA is transferred to a membrane which is a sheet of special blotting paper. The DNA fragments retain the same pattern of the separation as on the gel (blotting).
  
• The blot is incubated with many copies of a probe which is single-stranded DNA. This probe will form base pairs with its complementary DNA sequence and bind to form a ds DNA molecule. the probe is radioactive.
• The location of the probe is revealed when it is exposed to X-ray film (autoradiography).

Polymerase chain reaction or PCR consists of the following three steps:

1. Denaturation- The two DNA strands of template DNA separate from each other when heated to 92℃.

2. Annealing- The primers anneal to the 3’ end of single strands of DNA.

3. Extension- The primers are extended by DNA polymerase by the addition of nucleotides to form complete strands of DNA. Hence the sequence of steps is denaturation, annealing, extension.

• The word 'plasmid' was first coined by Joshua Lederberg in 1952. He used it to describe 'any extrachromosomal hereditary element'.
•  Lederberg first used the term in a paper he published describing some experiments he and his graduate student Norton Zinder conducted on Salmonella bacteria and its virus P22. 
• During the course of this work, they observed that virus particles could somehow pick up bacterial genes and transfer them to another host, a process they called transduction.
•  By the 1960s a number of plasmids had been identified. 
• This included fertility plasmids first observed, which carry the fertility genes necessary for bacterial conjugation. Another group were resistance (R) plasmids which carry the genes that encode resistance to antibiotics or poisons. It was an R plasmid (pSC101) that proved instrumental to the generation of the first recombinant DNA molecule.
•  Hence, Plasmid of a bacterium, Salmonella typhimurium was first time used in recombinant DNA technology. 
• So, the correct answer is 'Salmonella typhimurium'.

• A palindromic sequence is a sequence made up of nucleic acids within the double helix of DNA or RNA that is the same when reading from 5' to 3' on one strand and 5' to 3' on the other, complementary, strand.
•  It is also known as a palindrome or an inverted-reverse sequence. 
• The palindromic sequence for 5′ATTGCAAT3′ is 3′TAACGTTA5′.
• 
  
• So, the correct answer is '3′TAACGTTA5′

• Agarose is prepared from agar. Agar is extracted from marine red algae like Gelidium and Gracilaria. 
• Agarose is used in agarose gel electrophoresis. 
• Two types of electrophoresis are commonly carried out in molecular biology experiments. 
• One is PAGE (i.e., Polyacrylamide gel electrophoresis) and the other is agarose gel electrophoresis. 

• Gene cloning refers to a process in which we ligate a gene of interest to a vector (plasmid). 
• Recombinant DNA thus produced is introduced into a host cell (different organism) through transformation. 
• For example- the $$cry$$ gene extracted from bacteria, Bacillus thuringienesis is introduced into the genome of the cotton plant.