Question

1) what are molecular scissors.give example?

explain the role in recombinant dna technology with the help of example?
.
2) characteristics of cloning vector. describe?

why dna cannot pass through cell membrane.explain?

how bacterial cell is made competent to take up recombinant dna from the medium?
.

Answer 1

1. Restriction enzymes are also called 'molecular scissors' as they cleave DNA at or near specific recognition sequences known as restriction sites. These enzymes make one incision on each of the two strands of DNA and are also called restriction endonucleases.

2.
A cloning vector is a small piece of DNA, taken from a virus, a plasmid, or the cell of a higher organism, that can be stably maintained in an organism, and into which a foreign DNA fragment can be inserted for cloning purposes.

3. Since DNA is hydrophilic, it cannot pass through the cell membrane

Answer 2

Molecular scissors as the name indicates are used to cut molecules such as DNA molecule. These molecular scissors are called Restriction enzymes or DNA scissors.

Restriction enzymes are molecule specific, cut in a particular style and leave two types of ends of a DNA molecule.

In DNA recombinant technology, restriction enzymes  performs two functions:

- It cuts DNA molecule into small fragments leaving sticky or blunt ends  

- It cuts DNA suitable for the cloning purpose.

These are the characteristics of a cloning vector:

- A cloning vector must have a region of replication

- A cloning vector must has an acceptance for the selective marker

- Probably a small size so it inserts easily

- DNA cannot pass through a cell membrane because it is hydrophilic in nature and the lipid and membrane is hydrophobic in nature

- In order for recombinant DNA pass through bacterial membrane it needs pampering and special treatment with divalent cation such as Ca which allows its entry.