Recombinant DNA technology
Read the following passage carefully and answer the given questions
Biotechnology has been used by humans since times immemorial in the form of unmodified microbe mediated processes. However, rDNA technology uses genetically modified organisms and employs number of tools. The key tools are restriction enzymes, polymerase enzymes, ligases, vectors and the host organism. Restriction enzymes are also called as nucleases as they cut the DNA. Exonucleases cuts the DNA from the ends whereas endonucleases cuts the DNA at specific positions within the DNA. Endonucleases recognize a sequence of six base pairs called ‘recognition sequence’. Restriction enzymes cut both foreign DNA and vector DNA at specific point. Plasmids and bacteriophages are the commonly used vectors for transferring rDNA into the host organism. Vectors used now a days are engineered in such a way that help in easy linking with foreign DNA as well as selection of recombinants from non-recombinants. Maintenance of introduced DNA in the host and transfer of DNA to its progeny is one of the basic step of biotechnology.
Restriction endonuclease cuts each of two strands of DNA at specific point in form of a sequence called as -
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Palindromic sequence
A restriction endonuclease first finds its recognition sequence on the DNA. It then cuts each of the two strands at specific points. The recognition sequence is a palindromic nucleotide sequence. In DNA, a palindrome is a sequence of base pairs that reads the same on the two strands when both are read in the same direction, for example 5′-GAATTC-3′.
(1) UTR — Incorrect. UTR stands for untranslated regions. These are the parts at both ends of an mRNA that are not translated into protein.
(2) Satellite DNA — Incorrect. This is repetitive DNA that makes up a large part of the genome. It is not where restriction enzymes cut.
(3) Promoter — Incorrect. This is the site where RNA polymerase binds to begin transcription.
(4) Palindromic sequence — Correct. This is the sequence that restriction endonucleases recognise.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Restriction Enzymes –
