Question

Restriction endonucleases are useful in

• A. Crossing over
• B. Both A and B
• C. Breaking DNA at specific sites
• D. Creating sticky ends

Answer 1

The correct option is B Both A and B

Restriction endonuclease
Restriction endonucleases are the enzymes which cleave the DNA by digesting phosphodiester bonds at the specific sequences within the DNA. Examples include EcoR I.

Recognition sequence
Recognition sequence is the site where the DNA is cut by a restriction endonuclease.

For example, EcoR I is the restriction endonuclease that has 5’- GAATTC -3’ as its recognition sequence. It cuts the phosphodiester bond in the sugar-phosphate backbone in between guanosine monophosphate (G) and adenosine monophosphate (A).

Types of cleavage by REN
Restriction endonucleases cut DNA in two different ways as follows:
● Blunt cuts result in non-cohesive or blunt ends.
● Staggered cuts result in cohesive or sticky ends.●
Crossing over
The exchange of genetic material between the non-sister chromatids of homologous chromosomes during meiosis is called crossing over. It is catalysed by the enzyme recombinase.

Final answer
(C) Both A and B